national institute ofinterfaces of disparate materials. near-edge x-ray absorption fine structure...

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National Institute ofStandards and TechnologyWilliam JeffreyDirector

TechnologyAdministrationRobert CresantiUnder Secretary ofCommerce for Technology

U.S. Departmentof CommerceCarlos M. GutierrezSecretary Materials Science and

Engineering Laboratory

FY 2005 Programs andAccomplishments

PolymersDivisionEric J. Amis, Chief

Chad R. Snyder, Deputy Chief

NISTIR 7299

March 2006

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Certain commercial entities, equipment, or materials may be identified in this document in order todescribe an experimental procedure or concept adequately. Such identification is not intended to implyrecommendation or endorsement by the National Institute of Standards and Technology, nor is it intendedto imply that the entities, materials, or equipment are necessarily the best available for the purpose.

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Table of Contents

Table of Contents

Executive Summary ...................................................................................................................1

Technical Highlights

Direct Correlation of Organic Semiconductor Film Structureto Field-Effect Mobility .......................................................................................................2

Chaotic Flow to Enable Soft Nanomanufacturing ..............................................................4

X-ray Reflectivity as a Tool for Characterizing Pattern Shapeand Residual Layer Thickness for Nanoimprint Lithography .............................................6

Gradient Libraries of Surface-Grafted Polymers:Combi Tools for Surface Functionality ...............................................................................8

Quantifying Cellular Response to Biomaterials withMacromolecular Assembly ............................................................................................... 10

Nanometrology ........................................................................................................................ 13

Reference Specimens for SPM Nanometrology .............................................................. 14

Nanotube Processing and Characterization ...................................................................... 15

Combinatorial Adhesion and Mechanical Properties ........................................................ 16

Soft Nanomanufacturing ................................................................................................... 17

Defects in Polymer Nanostructures .................................................................................. 18

Critical Dimension Small Angle X-Ray Scattering ........................................................... 19

Nanoimprint Lithography .................................................................................................. 20

Materials for Electronics ......................................................................................................... 21

Polymer Photoresists for Nanolithography ....................................................................... 22

Organic Electronics ........................................................................................................... 23

Nanoporous Low-k Dielectric Constant Thin Films ......................................................... 24

Advanced Manufacturing Processes ...................................................................................... 25

NIST Combinatorial Methods CenterPioneer and Partner in Accelerated Materials Research ........................................... 27

Polymer Formulations:Materials Processing and Characterization on a Chip ...................................................... 28

Quantitative Polymer Mass Spectrometry ........................................................................ 29

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Table of Contents

Biomaterials ............................................................................................................................. 31

Combinatorial Methods for Rapid Characterizationof Cell-Surface Interactions .............................................................................................. 32

Cell Response to Tissue Scaffold Morphology ................................................................. 33

3-Dimensional In Situ Imaging for Tissue Engineering:Exploring Cell/Scaffold Interaction in Real Time ............................................................. 34

Broadband CARS Microscopy for Cellular/Tissue Imaging ............................................ 35

Molecular Design and Combinatorial Characterizationof Polymeric Dental Materials .......................................................................................... 36

Safety and Reliability ............................................................................................................... 37

Polymer Reliability and Threat Mitigation ......................................................................... 38

Polymers Division FY05 Annual Report Publication List ........................................................ 39

Polymers Division .................................................................................................................... 47

Research Staff ......................................................................................................................... 48

Organizational Charts .............................................................................................................. 57

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Executive Summary

I am pleased to report to you the results of astrong year for the Polymers Division. Our staff andresearcher collaborators continue to be acknowledgedfor their work in important areas, and in my summary,I would like to note some of these recognitions receivedthis year.

As an agency of the Department of Commerce, theNational Institute of Standards and Technology (NIST)focuses on work, often in collaboration with industry,to foster innovation, trade, security, and jobs. Thisyear, our efforts have been recognized by two awardsspecifically related to service to industry. Based onresearch, patenting, and technology transfer activitiesthat resulted in commercialization of polymericamorphous calcium phosphate compositions as dentalrestoratives, the Federal Laboratory Consortium (FLC)awarded Joseph Antonucci the 2005 FLC Award forExcellence in Technology Transfer. This prestigiousaward, judged by representatives from industry,state and local government, academia, and federallaboratories, recognizes outstanding work intransferring federal laboratory developed technologyto industry. Also this year, the Secretary of Commerceawarded the Department of Commerce Silver Medalfor Customer Service to the NIST CombinatorialMethods Center, specifically Eric J. Amis,Kathryn L. Beers, Michael J. Fasolka, AlamgirKarim, and Christopher M. Stafford, for excellencein transferring NIST-developed combinatorial andhigh-throughput measurement technologies to industry.Silver Medals are awarded to those individuals orgroups that demonstrate exceptional performancecharacterized by noteworthy or superlativecontributions that have a direct and lasting impactwithin the Department of Commerce.

Complementing these awards for service to industry,several scientists and engineers were acknowledged fortheir outstanding scientific careers. In a White Houseceremony on June 13, 2005, Michael J. Fasolka wasawarded the Presidential Early Career Award forScientists and Engineers (PECASE), the nation’shighest honor for professionals at the outset of theirindependent research careers. Mike was recognized forhis experimental and theoretical studies of nanostructuredpolymer films and for investigations extending thepower of next-generation scanned probe microscopytechniques on structures designed to provide quantitativemeasures of chemical, mechanical, and optoelectronicnanoscale material properties. At the 2005 AnnualMarch meeting of the American Physical Society(APS), Alamgir Karim was named a Fellow of Societyfor his pioneering research on polymer thin filmsand interfaces, polymer brushes, blend film phase

separation, thin film dewetting, pattern formationin block copolymer films, and the application ofcombinatorial measurement methods to complexpolymer physics. Acknowledging the breadth andimpact of his extremely productive career, NISTnamed Wen-li Wu a Fellow of the Institute. Wen-li wasspecifically recognized for the impact of his advances inmeasurement methods to assist industry, developmentsin the fundamentals of scattering, and significantscientific insights in polymer physics.

Executive Summary

Sampling of journal and book covers featuring researchfrom the Polymers Division

This annual report provides a sample of theoutstanding research from the scientists and engineersof the Polymers Division. I hope you enjoy readingour highlights in areas ranging from nanomanufacturingand nanofabrication to organic electronics andcombinatorial methods. As usual, only a portionof our work is included in this report, so pleasevisit www.nist.gov/polymers for more details.On our site, you can also download copies of anyof our publications.

As always, I welcome your comments.

Eric J. AmisChief, Polymers Division

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Direct Correlation of Organic Semiconductor Film Structureto Field-Effect Mobility

Organic electronics has dramatically emergedin recent years as an increasingly importanttechnology encompassing a wide array of devicesand applications including embedded passivedevices, flexible displays, and sensors. Deviceperformance, stability, and function critically dependupon charge transport and material interaction at theinterfaces of disparate materials. Near-edge x-rayabsorption fine structure (NEXAFS) spectroscopyis demonstrated as a powerful tool to quantifymolecular orientation, degree of conversion, andsurface coverage of solution-processed organicelectronics materials as a function of processingvariables and materials characteristics.

Dean M. DeLongchamp and Eric K. Lin

Organic electronic devices are projected torevolutionize new types of integrated circuits

through new applications that take advantage oflow-cost, high-volume manufacturing, nontraditionalsubstrates, and designed functionality. Progress inorganic electronics is slowed by concurrent developmentof multiple material platforms and processes and a lackof measurement standardization between laboratories.A critical need exists for diagnostic probes, tools, andmethods to address these technological challenges.

Recent efforts towards large-scale adoption oforganic electronics have focused on maximizing deviceperformance using new molecular designs and processingstrategies. In particular, tremendous effort has beendirected towards solution-based processing strategieswhere fabrication under ambient conditions is possible.Significant progress has been made towards formulationsfor ink-jet printing, spin-coating, or dip-coating. However,rational design and systematic progress are hindered byinsufficient correlations between organic semiconductorfilm structure and field-effect mobility in transistors.

Establishing direct correlations between the materialstructure and device performance has been challenging.These challenges are exemplified in recently developedsoluble precursor molecules shown in Figure 1 thatthermally convert into high-performance organicsemiconductors. Conversion of precursor filmsinvolves changes in structure at many levels. First, thechemical structure changes as solubilizing groups areremoved. Simultaneously, the molecules reorient withrespect to the substrate. Finally, large-scale molecularreorganization causes the film to become thinner,eventually reaching monolayer and sub-monolayer

coverage. Each of these changes strongly impacts theperformance of the semiconductor as an active layer inorganic field effect transistors (OFETs).

Figure 1: (Left) The conversion chemistry of an organicsemiconductor oligomer from an organic solvent soluble speciesto an insoluble organic semiconductor. (Right) NEXAFS spectraillustrating quantification of the degree of conversion as afunction of temperature.

To address these challenges, we developed andapplied near-edge x-ray absorption fine structure(NEXAFS) spectroscopy to quantify the degree ofconversion, molecular orientation, and surface coverage oforganic semiconductor thin films. NEXAFS spectroscopywas performed at the NIST/Dow soft x-ray materialscharacterization facility at the National SynchrotronLight Source (NSLS) of Brookhaven National Laboratory(contact: Daniel Fischer, NIST Ceramics Division).Carbon K-edge spectra were collected in partial electronyield (PEY) mode with a sampling depth of ≈ 6 nm.As cast, films of Pre-T6 in Figure 1 are approximately20 nm thick. We expect the conversion, orientation, anddefects within the sampling volume to closely matchthose of the mobile channel adjacent to the dielectriclayer of field effect transistor devices.

Figure 1 shows the conversion chemistry of anoligothiophene that is initially soluble in organicsolvents but undergoes thermolysis at elevatedtemperatures to become an organic semiconductor thatis insoluble in organic solvents. The carbon K-edgespectra in Figure 1 exhibit peaks that quantify thedegree of conversion. From these spectra, degrees ofconversion between the precursor and product can beobtained over the full practical range of annealingtemperatures. The NEXAFS spectra provide clearsignatures of the conversion chemistry even in verythin films.

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Figure 3: NEXAFS measurements of the orientation of themolecules as a function of temperature. The molecularorientation changes as the material undergoes chemicalconversion.Figure 2: The geometry of near-edge x-ray absorption fine

structure (NEXAFS) spectroscopy for the determination of theorientation of an oligothiophene organic semiconductor.

NEXAFS spectroscopy can also be used to measurethe molecular orientation of oligothiophene moleculesbecause the incident synchrotron soft x-rays arepolarized. The carbon–carbon π* and σ* resonantintensities (Figure 2) exhibit a strong angular incidencedependence that corresponds to an oriented resonancedefined by the spatial orientation of the final stateorbital. The π* intensity is largest at normal incidence(90 °), indicating that the conjugated plane of theproduct tilts away from the substrate in an “edge-on”orientation. The σ* intensity is greatest at glancingincidence (20 °), indicating that the long axis is normalto the substrate in a “standing up” orientation.

The changes in molecular orientation accompanyingthermolysis are quantified using a dichroic ratio, R,defined in Figure 2. R varies between +0.75 and –1.00,where a more positive R for the conjugated planeindicates increased tilt away from the substrate, whilea more negative R for the long axis indicates greatersurface-normality.

We observe four distinct orientation regimes duringannealing, as shown in Figure 3. First, the precursor isvertically oriented, and this weak orientation persistsuntil the treatment temperature of 125 °C exceeds themelting point at 110 °C. Second, R decreases from125 °C to 150 °C. Third, R increases greatly between150 °C and 200 °C, where the greatest increases in esterthermolysis are also observed, to plateau at 200 °C. Atthis point, both the conjugated plane and the long axis ofthe molecule are angled away from the surface as depictedin Figure 2. Finally, R decreases again at 300 °C indicatingthat the molecules relax into a more disordered orientation.This relaxation corresponds to coverage loss, which wasalso quantified with NEXAFS spectroscopy.

Figure 4: Graphical representation of the relationship betweenthe degree of conversion and molecular orientation with the fieldeffect mobility in a transistor device.

This example highlights NEXAFS as a powerful,nondestructive technique for detailed quantification ofthe structure and chemistry of nanometer thick organicsemiconductor films. These data provided insight into,and direct correlations with, the changes in electronicproperties. NEXAFS will continue to provide apowerful measurement platform for the systematicinvestigation of organic semiconductors and conductors.

For More Information on This Topic

D.M. DeLongchamp, S. Sambasivan, D.A. Fischer,E.K. Lin, P. Chang, A.R. Murphy, J.M.J. Frechet,and V. Subramanian, “Direct Correlation of OrganicSemiconductor Film Structure to Field-Effect Mobility,”Advanced Materials 17, 2340–2344 (2005).


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Chaotic Flow to Enable Soft Nanomanufacturing

intersecting channels is a cross flow mixer (CFM) asshown in Figure 1. To generate chaos in this geometry,flow in the two perpendicular channels of the cell isdriven sinusoidally, and 90 ° out of phase. Thus,successive sets of temporal streamlines cross each otherevery quarter period at the center of the geometry, asrequired for chaos per the crossing streamline principle.

Conventional methods fail in the analysis ofchaotic flow. Thus, in order to evaluate the abilityof a flow configuration to produce chaotic motion,the deformation of material lines or surfaces composedof passive tracer particles are tracked in a manneranalogous to flow experiments using tracer dyes.The deformation of a material line composed of 25,000individual particles in the CFM is shown in Figure 1.The material line is initially stretched out along thex-axis (Figure 1a), and the stretching and folding of thematerial line gradually leads to the particle dispersionpattern shown in Figure 1d.

From the deformation of the material line, we mayidentify three signatures of chaos. First, from the figurewe see that the particles tend to evolve to a formationin which they are randomly dispersed in a closedsurface within the flow domain — this is a signatureof Hamiltonian chaos. A second signature is theexponential stretching of the line of particles. A semi-log plot of L/L0 vs. time (where L is the length of theline) shows that the data are very closely fit by anexponential relationship with a positive exponent valueof 0.41, which can be thought of as an “effective” or


The challenge of generating nanoscale functionalstructures from soft materials (polymers, colloidalsuspensions, dispersions) requires innovativemanufacturing strategies. In our program, we utilizemicrofluidics to combine self-assembly technologieswith top-down manufacturing methods. Propermixing of components emerges as a crucial issue inmicrofluidic manufacturing operations due to thebreakdown of conventional techniques. Our objectiveis to utilize the concept of “chaotic flow” for propermixing of components.

Frederick R. Phelan, Jr. and Steve Hudson

Acentral goal of nanomanufacturing is to combine top-down manufacturing techniques with bottom-up

methodology in a flexible and robust fashion. We aredeveloping a portfolio of microfluidic-based techniquesto accomplish this objective, focusing on particleself-assembly and in-situ monitoring of manufacturingoperations.

An outstanding issue in a wide variety ofmanufacturing operations is the efficient mixing ofliquid phase chemical species. Due to the small lengthscales of the flow channels (from 1 µm to 200 µm),the typical turbulent mixing, which is extensivelyutilized in larger scale flows, cannot be achieved, andnew schemes must be developed. It is known thatchaotic flow is the most efficient way of mixing outsidethe turbulent regime. In microfluidics, little is knownabout how to generate chaotic flow and how to bestmeasure it. Here we describe numerical methodologiesthat demonstrate chaotic flow in microfluidicgeometries. We find the signatures of chaos viadetailed analysis of the flow fields and show that wecan generate chaotic flow for both pressure-drivenand electric field-driven flows.

To generate chaos in microfluidic flows, we exploitthe principle of temporally crossing streamlines whichstates that a necessary condition for generating chaoticflow is that the streamlines at time t must intersect thestreamlines at some later time t + ∆t at one or morepoints in the flow domain. The crossing streamlinesconsidered in this work are distinctly different fromthose considered in previous studies. We consideredhere the case of flow in intersecting channels, wheretemporal variations are introduced through the use ofoscillatory flow boundary conditions.

Both batch and continuous mixing have beenstudied, as they both have direct relevance to processesof interest. For batch mixing, the simplest case of

Figure 1: Chaotic mixing in a pressure-driven cross flow mixer(CFM), for a Strouhal number of 1.28 after 15 cycles. A materialline composed of 25,000 particles is initially stretched out alongthe x-axis. The stretching and folding of the material line leads tokinematic particle dispersion, a signature of chaotic flow.

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finite-time Lyapunov exponent. A final signature ofchaos is that the flow is ergodic — that is, the dispersionpatterns observed after a large number of cycles fordifferent particle initial conditions are indistinguishablefrom one another. Simulations with different particleinitial conditions confirm the ergodic property.

The onset of chaotic behavior in the CFM iscontrolled by a dimensionless number called theStrouhal number (St) which relates the distance aparticle moves in a half-cycle to the width of the flowchannel. Chaos sets in at St ≈ 0(1), and the size of thechaotic region and magnitude of the Lyapunov exponentgrows continually with increasing St. Further, weidentified that the mechanism for chaotic flow in the CFMis a periodic combination of stretching and rotation,making the system a continuous tendril-whorl (TW)type flow. This differentiates it from other studies usingoscillatory boundary conditions as they produce discrete(non-continuous) TW flows resulting in the requirementof greater geometric complexity to mix the fluid streams.

Clearly, the configuration may also be used with adiscontinuous throughput stream, to mix componentson a semi-batch basis.

The results discussed above are for pressure-drivenflow. However, an important means of transportingfluid in microfluidic geometries is through the use ofelectroosmotic flow (EOF), especially in the emergingarea of droplet-based microfluidics. In the EOF flows,temporally crossing streamlines are generated byapplication of out-of-phase sinusoidal voltage gradients.

We find that chaotic mixing can also be obtained inEOF, for both batch and continuous flow. Stretching ofa material line for batch mixing via EOF is shown inFigure 3a and for continuous mixing in the star-cellin Figure 3b. Chaotic particle dispersion and positiveLyapunov exponents are observed for both cases.In terms of experimental implementation, the EOFdriven flow offers several advantages. First, the endsof the oscillatory channels are closed, so there are noinflow and outflow to handle. Second, the oscillatoryflow channels can be made shorter for EOF, as it wasfound that the critical Strouhal number for the onset ofchaos decreased and the effective Lyapunov exponentincreased, as the ratio of the length to the width ofthese channels was made smaller.

Experimental testing of these results is currentlybeing conducted as well as an investigation of theinterplay between diffusion and chaotic flow.


F.R. Phelan, Jr., N.R. Hughes, and J.A. Pathak,“Analysis of the Mechanism for Chaotic Mixing inOscillatory Flow Microfluidic Devices,” submitted toPhys. Rev. Lett., 2005.

F.R. Phelan, Jr., N.R. Hughes, and J.A. Pathak,“Mixing in Microfluidic Devices Using OscillatoryChannel Flow,” submitted to Physics of Fluids, 2005.

Figure 2: Chaotic mixing in the star-cell geometry is shown fora Strouhal number of 1.28 and a velocity ratio of 0.125 after10 cycles. In the star-cell, chaos is generated by the oscillatoryflow in transverse channels, and the lateral flow providesthroughput for continuous mixing.

Figure 3: a) Chaotic mixing in an EOF driven cross-flowmixer (CFM), for a Strouhal number of 0.64 after 10 cycles.b) Chaotic mixing in an EOF driven star-cell mixer, for a Strouhalnumber of 2.04 and a velocity ratio of 0.125 after 10 cycles.For both cases, the oscillatory flow is driven by the applicationof out-of-phase sinusoidal voltage gradients along the majoraxes of the cell.


We now discuss continuous chaotic mixing,which will be relevant to any continuous high-speednanomanufacturing operation. In a configurationcalled the star-cell geometry (see Figure 2), a lateralcontinuous channel flow (from left to right) iscombined with the oscillatory cross flow. The mixingcharacteristics in the star-cell are a function of bothSt and the ratio of the continuous-to-oscillatory velocity.The deformation of a material line passing through theoscillatory section is shown in Figure 2. The particledispersion in the downstream channel indicates thatthe competition between the two flows is quiteeffective in producing a well-mixed effluent.

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X-ray Reflectivity as a Tool for Characterizing Pattern Shapeand Residual Layer Thickness for Nanoimprint Lithography

Nanoimprint lithography has the potential for highthroughput patterning with an ultimate resolutionof better than 10 nm. With these length scales,our ability to pattern greatly exceeds our ability toquantitatively evaluate the quality of the patterningprocess. Measurements that can evaluate the fidelityof the pattern transfer process and the overall qualityof the imprint are critical for realizing the fullpotential of nanoimprint patterning techniques.

Christopher L. Soles and Ronald L. Jones

Nanoimprint Lithography (NIL) is a form of printingwhereby nanoscale features are written into a

master, typically Si, quartz, or some other hard material,using a slow, high-resolution technology such ase-beam lithography. The master can then be rapidlyand repeatedly stamped into a softer resist film. Thisreplication technique is a cost-effective way to combinethe high-resolution patterning of e-beam lithographywith the throughput of a stamping or printing process.

Figure 1: Schematic of nanoimprint lithography process.

The resolution of NIL is comparable to that of e-beamlithography, and features as small as 10 nm have beendemonstrated. However, it is difficult to quantify andcontrol dimensions in such small features. To takefull advantage of the potential resolution of NIL, high-resolution shape metrologies are critical. Furthermore,during the imprint process, the master is unable to fullydisplace the resist and make contact with the substrate.This leaves a residual layer of resist between the featuresthat can be removed with a reactive ion etch. However,this also laterally erodes the feature width. Minimizationof this lateral trimming and control of the final featuresize requires a precise knowledge and optimization of theresidual layer thickness. In short, two of the most pressingissues facing NIL include: (1) quantifying the fidelitywith which the patterns in a master are transferred tothe imprinted film; (2) quantifying the residual layerthickness. Here we adapt specular x-ray reflectivity(SXR) to quantify both the fidelity of pattern transferand the residual layer thickness with nanometerprecision in NIL masters and patterns.

SXR is a well-established method for measuring boththe thickness and the density as a function of depth intoa thin film. Here we extend the use of SXR to patternedfilms where the lateral length scales of the patterns are inthe sub µm range. As the cartoon in the inset of Figure 2indicates, the master or mold is comprised of a singlematerial, SiOx (black). However, the reflectivity, R, ischaracteristic of a bilayer film, a smooth “gray” filmon the black SiOx. The strong, periodic Kiessig fringesand the two critical angles Qc are consistent with asmooth bilayer structure. The red line through the blueexperimental data points is a fit to such a smooth bilayermodel where the density of the gray layer is an averageof the white and black (open and fully dense) regions ofthe pattern while the thickness of the gray layer equalsthe pattern height. The SXR averages density overlength scales that are apparently larger than thelateral-length scales of the topology.

Figure 3: SXR data from a polymeric resist imprint created fromthe master characterized in Figure 2.

Figure 2: SXR data from a NIL master. Q=2π /λ sin(θ) with λthe wavelength of the incident radiation and θ the grazing angle.


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Analogous SXR measurements are repeated ona polymeric resist imprint created from the master above.These reflectivity data are shown in Figure 3. Consistentwith the mold, the reflectivity from the imprint on theSiOx substrate shows characteristics of a smooth trilayerstructure. The Kiessig fringes show a beating of multipleperiodicities, and three Qc’s are observed. The cartoon inthe inset indicates black for the SiOx substrate, dark grayfor the pure resist, and light gray for the patterned regionof the resist. As before, the light gray is an averageof the dark gray (solid) and white (open) domains.The red solid line through the blue experimental datais a quantitative fit to a smooth trilayer model.

here. Through these density variations as a function ofpattern height, the pattern cross-sections can be evaluated.

The scattering length density Qc2 profiles as afunction of distance vertically through the patterns (z)are shown in Figure 4. Qc2 is directly proportional tomass density, and the horizontal dotted lines indicate thevalues of Qc2 for the pure SiOx and the resist. On thedensity profile for the imprint, the region (1281 ± 10) Åwide matching the full density of the resist representsthe residual layer thickness. To the left of this is aregion of reduced density that is (1730 ± 10) Å wide.This is the height of the pattern. One can also see howthe depth of the patterns in the mold equals the height ofthe imprinted pattern; this indicates complete mold fill.Such a comparison of the mold and imprint can be usedto quantify the fidelity of pattern transfer.

There are two blue vertical arrows drawn next to theprofile of the imprint. Line “l” starts at Qc2 = 0 and extendsvertically to the intersection of the imprint profile. Line“s” starts at this same intersection and extends verticallyto the Qc2 value corresponding to the density of the pureresist. At any z, the ratio l:s defines the line-to-space ratioof the pattern. This ratio increases with z for the imprint,indicating that the pattern is narrow on the top andbroadens near the residual layer. A similar constructioncan be made for the mold although the lines are not shown

Figure 5: Comparison of mold and imprint profiles. The red andblue data points indicate the line shape profiles from the SXR forthe mold and imprint, respectively. The corresponding physicalmodels that best fit the data are indicated by the solid lines. Forthe sake of clarity, the mold data are shown on the left side of oneof the features while the imprint data are shown on the right.

These line width variations as a function of patternheight are relative, and one cannot define an absoluteline width from the SXR alone. An external calibrationof the line width, space width, or pattern pitch is neededto convert the relative line-to-space variations intoabsolute values. To illustrate this, critical-dimensionsmall angle x-ray scattering (CD-SAXS) was used toquantify the pattern cross-section. A trapezoidal lineshape provided an excellent fit to the CD-SAXS data.Figure 5 is the resulting comparison that shows howwell the imprint features fit into the mold, indicating anexcellent fidelity of transfer. The pitch of 1945 Å fromthe CD-SAXS models is used to transform the relativeline-to-space ratios from the SXR density profiles intophysical line widths. These SXR data points exactlycoincide with the solid lines for the CD-SAXS models,showing excellent agreement in terms of both patternheight and the trapezoid side wall angles β.

In summary, SXR is a powerful metrology toquantitatively characterize the residual layer thicknessand the relative line-to-space ratio variations as afunction of pattern height. If one of the widths (lineor space) or pattern pitch is known by some othertechnique (CD-SAXS, SEM, AFM, etc.), these relativeline-to-space ratios can be quantified in terms of anabsolute length scale to completely define the patterncross-section. Applying this metrology to both themold and the imprint makes it possible to not onlyquantitatively measure the residual layer thicknessbut also assess the fidelity of pattern transfer.


H.J. Lee, C.L. Soles, H.W. Ro, R.L. Jones, E.K. Lin,W.L. Wu, and D.R. Hines, Appl. Phys. Lett. 87, 263111(2005).

Figure 4: Scattering length density profiles as a function ofdistance vertically through the patterns for the mold (red) and theimprint (blue). The horizontal axis is arbitrarily assigned, so themold substrate on the left (≈ 0 Å) faces the imprint substrate onthe right (≈ 3100 Å) with the mating pattern region in between.


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Gradient Libraries of Surface-Grafted Polymers:Combi Tools for Surface Functionality

Advanced applications, such as friction andwear management in microelectromechanicalsystems (MEMS), adhesion promotion for coatings,protein adsorption control in biomaterials, andenvironmentally responsive surfaces for sensorsrequire tunable, well-defined interfaces. Layersof grafted polymers provide means for physicallyrobust, chemically versatile surface functionalization.While recent advances in controlled polymerizationenable grafted polymers that exhibit many typesof architecture and composition, identifying theoptimal grafted system for a given applicationcan be difficult, time consuming, and expensive.

Kathryn L. Beers and Chang Xu

Through the NIST Combinatorial Methods Center(NCMC), the Polymers Division has developed

new tools for probing the optimal molecular- tomicro-scale properties of grafted polymer systems.These methods employ microfluidic technology todeliver tailored mixtures and sequences of monomersto an initiator-functionalized surface. The resultinggrafted polymer libraries exhibit gradual, systematicchanges in composition, chain length, and architecture.Gradients of grafted block copolymers prepared viathese techniques reveal composition regimes that“switch” their surface properties in response to solventexposure. Moreover, our unique method for preparingstatistical copolymer composition gradients providescomprehensive maps of complex surface chemistrythat were previously impossible.

Using shallow channels (< 500 µm in height) toconfine fluids over initiator-functionalized surfacessuppresses mixing. By controlling the compositionof fluids pumped into the channels, and the length oftime of surface exposure, gradients in composition orrelative molecular mass are produced. This technique,micro-channel confined surface initiated polymerization(µSIP), was used to produce a variety of combinatorialsurfaces as shown in Figure 1 and enables systematicmeasurement of polymerization parameters.

Figure 2: A) Film thickness of gradient poly(n-butyl methacrylate)(pBMA) homopolymer (closed symbols) and poly(n-butylmethacrylate-b-N,N-dimethylaminoethyl methacrylate)(p(BMA-b-DMAEMA)) (open symbols). B) Percentage growth ofPDMAEMA block on the gradient surface with respect to a bareinitiator-modified surface.

Figure 1: Examples of polymer libraries prepared usingmicro-channel confined surface initiated polymerization (µSIP)and ATRP of methacrylates.

The initiation efficiency of a homopolymer on asurface affects both the density and relative molecularmass distribution of the second block that can begrown from it. Figure 2A shows data from a relativemolecular mass gradient of poly(n-butyl methacrylate)(pBMA) that was uniformly chain extended withpoly-(N,N-dimethylaminoethyl methacrylate)(pDMAEMA) to form the block copolymer poly(n-butylmethacrylate-b-N,N-dimethylaminoethyl methacrylate)(p(BMA-b-DMAEMA)).

A relative measure of initiation efficiency wasobtained as a function of molecular mass of the bottompBMA block by normalizing the change in thickness ofp(BMA-b-DMAEMA) to the thickness of pDMAEMAgrafted directly from a separate initiator-functionalizedsurface. The data in Figure 2B show that the efficiencyremains above 90 % for pBMA with a thickness of 15 nmor less, indicating that comparative measurements ofblock copolymer behavior are possible below thisthickness. Using this information, a series of surface-grafted block copolymer gradients was prepared withpBMA as the bottom block and pDMAEMA as thetop block.

Figure 3A shows data from three gradient surfaces withdifferent, uniform bottom block thicknesses and similargradients in top block thickness. The surface energy, as


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measured by water contact angles, of the air interfaceof the brush layer can be controlled by exploitingsolubility differences between pBMA and pDMAEMA.In water, the pDMAEMA chain segments swell, whilethe pBMA segments collapse. After drying, the surfaceexhibits the same water contact angle as pDMAEMAhomopolymer brushes as long as there is at least(2 to 3) nm of pDMAEMA in the copolymer to coverthe surface (Figure 3B, open symbols). After exposureto hexanes, which will swell the lower pBMA chainsegments and collapse the pDMAEMA segments,the pBMA segments can be expressed at the surface,covering the pDMAEMA segments. The mainrequirement for this “surface response” is a ratioof pBMA to pDMAEMA sufficient for completerearrangement and pBMA surface coverage, asshown in Figure 3B. At intermediate ratios, a partialexpression of the lower pBMA produces a rangeof intermediary surface energetics.

Determination of the composition range forthis transition, its dependence on chain length, andoptimization of the response region were all possibleusing the gradient method. Performing measurementson single gradient specimens reduced variability andilluminated the subtlety and sensitivity of the transitionto relative molecular mass and copolymer mass fraction.

Well-defined surface chemistry has been used tocontrol structure formation in thin films and fluid flow inmicrofluidic devices. To map and optimize these effects,controlled, smooth gradients in chemical expression havebeen produced with self assembled monolayers (SAMs).However, SAM surfaces offer a limited number offunctional groups and modest stability over time. Polymerbrush layers provide means to expand the chemicaldiversity of surface gradients while creating a layer ofcarbon chains to protect the hydrolytically unstable siliconoxygen bonds that covalently link the chains to the surface.A compelling case is a gradient in statistical copolymercomposition, for which we have recently developed afabrication strategy using µSIP.

Figure 4: A) Stability of a monomer composition gradientinside a microchannel monitored by Raman spectroscopy at 0 h(black squares) and 2 h (red circles). B) Water contact angle ofp(BMA-co-DMAEMA) as a function of position on a gradientof composition prepared from the solution gradient mappedin Figure 4A.

A gradient in solution composition wasconstructed such that the monomer feed was variedfrom (2 to 98) % by volume DMAEMA relativeto BMA along the channel (Figure 4A). Both theestablishment and stability of the solution gradientwere measured by Raman spectroscopy, indicatingthat the gradient persisted for at least 2 h, while thereaction time was only 40 min. Figure 4B showswater contact angle measurements taken alongthe polymerized gradient, which reveal a smoothtransition from the surface energetics characteristicof pDMAEMA to those of pBMA. The changingcomposition of the polymer brush was alsocharacterized by NEXAFS measurements (data notshown). Unlike the block copolymers, the statisticalcopolymer surface does not switch the surfaceexpression with exposure to different solvents.The chemical gradient is trapped by the intimatelymixed nature of the copolymerization.

Fabrication of grafted tapered copolymers,which exhibit a gradual change in compositionalong the polymer chain, has also been demonstrated.An upcoming publication will describe the fabricationand properties of this unique system. In addition,future work includes combining micro-scale patterningwith the chemical gradient brushes for the fabricationof calibration specimens, as well as expandingthe method to additional monomer types andpolymeriziation mechanisms to make µSIP aversatile, widely applicable measurement tool.


C. Xu, T. Wu, C.M. Drain, J.D. Batteas, andK.L. Beers, Macromolecules 38, 6–8 (2005).

C. Xu, T. Wu, J.D. Batteas, C.M. Drain, K.L. Beers,and M.J. Fasolka, Appl. Surf. Sci. 252, 2529–2534 (2006).

Or visit the NCMC website (www.nist.gov/combi)

Figure 3: A) Thickness profiles of three gradient surfaces ofp(BMA-b-DMAEMA) prepared via µSIP. B) Solvent responsebehavior of p(BMA-b-DMAEMA) in water (open symbols) andhexanes (closed symbols) as a function of relative molecularmass of the top (pDMAEMA) block for three thicknesses of pBMAbottom block. Colors and symbols correlate solvent responseprofiles to samples mapped in Figure 3A. Lines drawn to aidreader’s eyes.


10

Quantifying Cellular Response to Biomaterials withMacromolecular Assembly

In order to move beyond empirical trial and errorinto design, biomaterials development is in urgentneed of reliable measurement standards andtechniques. These depend on the ability to quantifyprotein-mediated cellular response to technologicallyrelevant materials. We introduce a multi-molecularassembly of polymer/protein gradients as a techniqueto do just that. We demonstrate its potential tostudy interactions between fibroblasts, a particularpolymeric biomaterial, and fibronectin. However,we emphasize the ease of extending the techniqueto quantify interactions between a variety ofbiomedically relevant polymers, proteins, and cells.

Ying Mei, Lori Henderson, and Jack R. Smith

The competing issues of reproducibility andapplicability in measurements of cellular response

must be addressed by the biomaterials industry.Information generated by experimental testing needsto be quantitatively robust, however, the inherentvariation in the response of any biological organismand the complexity of protein/surface interactions areproblematic; most currently used biomaterials lack ahomogeneous or well-determined surface; efforts toquantify biological response have focused on usingregular and simplified model surfaces, such as those ofself-assembled monolayers (SAMs); and the fact thatpolymers of direct interest in biomedical applicationscannot be incorporated into SAMs renders the practicalapplicability of these results questionable.

To address these issues, we synthesized a surfaceincorporating a biomedically relevant polymer,poly(2-hydroxylethyl methacrylate) [poly(HEMA)],through a multi-macromolecular assembly (MMA).We use automated fluorescent microscopy todemonstrate that the system is sufficiently well-definedfor quantifiably repeatable measurements of cellresponse and protein adsorption. We have describedthe latter phenomenon to a high degree of accuracywith a simple, geometric model.

Preparation of the MMA gradient sample isconceptually simple. First, a SAM of octyltrichlorosilane(OTS) is deposited on a silicon substrate by evaporation.Then, the wafer is placed upright in a reaction vesselwhere atom transfer radical polymerization (ATRP)initiator is pumped in at a specific rate (Figure 1a).Filling from the bottom creates a differential exposureto the initiator along the length of the sample parallelwith the walls of the vessel. This leaves a graftingdensity (σ) gradient of poly(HEMA) on the surface of

Figure 2: FN density vs. σ. Black data points are averagedresults from three gradient or twelve uniform (non-gradient)samples. FN density was estimated from measurements of thethickness of the adsorbed layer obtained via ellipsometry.Data in red were obtained from the geometric model ofpoly(HEMA) surface coverage.

Figure 1: A) Schematic illustration of the reaction vessel usedin the preparation of the gradient of polymerization initiator.B) Schematic illustration of poly(HEMA) conformational changefrom “mushroom” regime to “brush” regime on the gradientsurface. Poly(HEMA) is represented in black, while FN isschematically represented by the multi-colored structures.OTS is represented as an unfilled rectangle. ATRP initiatoris represented as a gradually filled rectangle.

the sample in the direction parallel to the walls of thereaction vessel (Figure 1b). Subsequently, the sampleis removed from the vessel and exposed to fibronectin(FN) solution. Later, the samples are seeded withfibroblast NIH-3T3 cells in medium.


11

Although combinatorial studies have already receivedsignificant attention in biomaterials research, their useis limited by the lack of a complete toolbox includingstreamlined sample preparation, characterization,bioactivity assay, and data analysis. We demonstratethe uses of gradient preparation technology, controlledcell culture, automated fluorescence microscopy andquantitative image analysis to generate a database forcombinatorial investigation of the effect of σ on celladhesive protein adsorption, fibroblast adhesion,and spreading.

In addition, adsorption profiles of differentbiological macromolecules and their interactionswith surface chemistries can be quantified bysimply replacing FN in the pre-adsorption partof this experiment. In fact, we are currentlyusing the approach presented here to investigatepoly(HEMA)/fibrinogen gradients and will do sowith other extracellular matrix proteins. MMA hasfew limitations regarding the variety of cells in theexperiment; therefore the combination of MMAtechnology, quantitative fluorescence microscope,and controlled cell culture provides the foundationsfor the cell informatics about material properties,protein adsorptions, and cellular responses.

Reference

1. S.J. Sofia, V. Premnath, and E.W. Merrill,Macromolecules 1998, 31, 5059.


Y. Mei, T. Wu, C. Xu, K.J. Langenbach, J.T. Elliott,B.D. Vogt, K.L. Beers, E.J. Amis, and N.R. Washburn,Langmuir 21, 12309–12314 (2005).

Figure 4: a) Histogram of cell size on various FN coatedsurfaces: bare OTS (green), low (red), high (blue, purple).b) Inset: Change in cell spreading (area) with σ.

FN adsorption (FNads), measured using variableangle spectroscopic ellipsometry, was found to varysigmoidally with σ (Figure 2). A simple geometricmodel, in which FNads is proportional to the area of thesurface left uncovered by polymer, predicted the formerwith a r2 coefficient of 0.97 (Figure 2). In the model,the surface coverage of poly(HEMA) is estimated fromσ obtained from ellipsometry measurements performedprior to FN exposure and the radius of gyration ofpoly(HEMA).[1]

Figure 3: Fluorescence microscopy image of stained fibroblastNIH-3T3 cells seeded on a FN pre-coated σ gradient sample.Although the sample is contiguous, its microscopy image here issplit into three segments so that changes in cell morphology withdistance/σ will be visible on the page. Distance in the Figureis measured from the end of the sample closest to the top of thereaction vessel (i.e., from the end of the sample with lowest σ)in Figure 1a.

Cellular response varied dramatically along thesurface of the poly(HEMA)/FN gradient (Figure 3).As cell spreading (Figure 4) and FNads (Figure 2) wereboth found to vary sigmoidally with σ, the high degreeof correlation between the two phenomena was clearlydemonstrated. The onset of maximal cell adhesion andcell spreading were measured at FNads of 50 ng/cm2

and 100 ng/cm2, respectively. Further, a ten-foldincrease in σ caused a change in the average area offibroblasts (i.e., cell spreading) from (1238 ± 704 to377 ± 216) µm2. The standard deviation representsthe variation of the measurement over 12 trials.

Results obtained on three separate gradientsamples were in quantitative agreement with thoseobtained on uniform (i.e., non-gradient) samples ofsimilar composition (Figure 2 and 4). This showsthe capability of the former to dramatically advancethe pace of biomedical materials research throughsimultaneous testing of multiple compositions.


13

Program Overview

Nanometrology

Nanotechnology will revolutionize and possiblyrevitalize many industries, leading to new and improvedproducts based on materials having at least one dimensionless than 100 nm. The federal government’s role inrealizing the full potential of nanotechnology is coordinatedthrough the National Nanotechnology Initiative (NNI),a multi-agency, multi-disciplinary program that supportsresearch and development, invests in a balancedinfrastructure, and promotes education, knowledgediffusion, and commercialization in all aspects ofnanoscale science, engineering, and technology.NIST’s unique and critical contribution to the NNI isnanometrology, defined as the science of measurementand/or a system of measures for nanoscale structuresand systems. NIST nanometrology efforts focuson developing the measurement infrastructure —measurements, data, and standards — essential toadvancing nanotechnology commercialization.This work provides the requisite metrology toolsand techniques and transfers enabling measurementcapabilities to the appropriate communities.

MSEL plays a vital role in nanometrology work atNIST with efforts in four of the seven NNI ProgramComponent Areas — Instrumentation Research,Metrology and Standards for Nanotechnology;Nanomaterials; Nanomanufacturing; and FundamentalNanoscale Phenomena and Processes. Innovativeprojects across MSEL are defining and addressingthe forefront research issues in these areas.

Instrumentation Research, Metrologyand Standards for Nanotechnology

R&D pertaining to the tools needed to advancenanotechnology research and commercialization.The design, development, and fabrication of nanodeviceswill require nanomechanical measurements that are rapid,accurate, predictive, well-understood and representativeof a device or system’s environment in real time. MSELis addressing this need by developing instrumentation,methodology, reference specimens and multi-scalemodeling approaches to quantitatively measure mechanicalproperties such as modulus, strength, adhesion, andfriction at nanometer-length scales. This year, novelinstruments for measuring adhesion and friction forcesbetween surfaces and nanoparticles were developed jointlywith industrial partners. Quantitative maps of elasticmodulus were obtained by innovative methodologies basedon atomic force microscopy and strain-induced elasticbuckling instability. To address the need for quantifyingmeasurements made with widely-used commercialnanoindentors and scanned probe microscopyinstruments, MSEL is developing reference specimensand SI-traceable force calibration methodology.

NanomaterialsResearch aimed at discovery of novel nanoscale

and nanostructured materials and at a comprehensiveunderstanding of the properties of nanomaterials.Among the many classes of nanomaterials, nanotubeshave received great attention due to their remarkablephysical properties relevant to many applications.In response to needs expressed by industry and otherfederal agencies, MSEL has embarked on a new effortto develop a suite of metrologies and standards aimedat characterizing key structural features and processingvariables of carbon nanotubes. These include dispersion,fractionation, orientation, alignment, and manipulationof individual single-walled nanotubes, all critical toestablishing efficient bulk processing schemes to meetthe imminent high demand for carbon nanotubes.

NanomanufacturingR&D aimed at enabling scaled-up, reliable,

cost-effective manufacture of nanoscale materials,structures, devices, and systems. Nanoimprint lithography(NIL) is rapidly emerging as a viable high-throughputtechnique for producing robust structures with apatterning resolution better than 10 nm. MSEL isdeveloping metrologies that are crucial to advancingNIL as an industrial patterning technology for theelectronics, optics, and biotechnology industries.The current focus is on characterizing shape andthe fidelity of pattern transfer, two key factors inachieving widespread commercial application of NIL.

Fundamental NanoscalePhenomena and Processes

Discovery and development of fundamental knowledgepertaining to new phenomena in the physical, biological,and engineering sciences that occur at the nanoscale.The magnetic data storage industry needs the ability tomeasure and control magnetization on nanometer lengthscales and nanosecond time scales to meet increasingdemands for reduced size and increased speed of devices.MSEL is developing measurement techniques to elucidatethe fundamental mechanisms of spin dynamics anddamping in magnetic thin films. Work this year hasfocused on measurements of the effects of interfacesand interface roughness on magnetization dynamics andmagnetic characterization of edges in magnetic devices.

Through these and other research activities,MSEL is maintaining its committed leadership indeveloping the measurement infrastructure forcurrent and future nanotechnology-based applications.

Contacts: Alamgir Karim; Kalman Migler

14

Engineering of nanomaterials, biomaterials, andorganic electronic devices hinges on techniquesfor imaging complex nanoscale features. In thisrespect, new Scanned Probe Microscopy (SPM)methods promise mapping of chemical, mechanical,and electro-optical properties, but these techniquesgenerally offer only qualitative information.Our reference specimens, fabricated with acombinatorial design, calibrate image data fromemerging SPM methods, thereby advancing thesenanometrology tools.

Michael J. Fasolka

Anew generation of SPM techniques intend to measure chemical, mechanical, and electro/optical

properties on the nanoscale. However, contrast in newSPM images is difficult to quantify since probe fabricationcan be inconsistent, and probe/sample interactions are notunderstood. Our research at the NIST CombinatorialMethods Center (NCMC) provides reference specimensfor the quantification of next-generation SPM data.Using a gradient combinatorial design, our specimensgauge the quality of custom-made SPM probes andcalibrate SPM image contrast through “traditional” surfacemeasurements (e.g., spectroscopy and contact angle).

Nanometrology

Reference Specimens for SPM Nanometrology

Figure 2: Demonstration of ∇µp specimen. SPM frictioncontrast (κ) vs. surface energy (γ) differences obtained withprobes of different chemical quality. The red arrow marks theγ-difference sensitivity of a UV-ozone cleaned probe.

Figure 1: Schematic illustration of the ∇µp for calibration ofchemically sensitive SPM techniques. Blue “droplets” illustratewater contact angle measurement along the calibration strips.

of the matrix. Accordingly, traditional measurements,e.g., water contact angle, along these fields relatethe chemical contrast in the ∇µp to known quantities,e.g., surface energy differences.

Figure 2 demonstrates the utility of the ∇µp specimenfor SPM data calibration. This plot was generated from aseries of SPM friction images acquired along the gradedpattern. A frictional contrast parameter, κ, which reflectsmeasured friction force differences between the lines andmatrix, was extracted from each image. To create acontrast calibration curve, κ is plotted against surfaceenergy data derived from water contact measurementsalong calibration fields. As shown in Figure 2, thecombinatorial ∇µp provides, in a single specimen, a full-spectrum relationship between SPM friction force andsurface energy. As shown through the three curves, thespecimen also enables direct comparison between differentprobe functionalization strategies. Moreover, the curvesilluminate the minimum γ-difference detectable by a givenprobe (where κ → 0), i.e., its chemical sensitivity.

Our fabrication route for the ∇µp, and its use asa reference specimen for emerging SPM techniques,is the subject of an article published in Nanoletters(2005, ASAP).

Contributors and Collaborators

K.L. Beers, D. Julthongpiput (Polymers Division,NIST); D. Hurley (Materials Reliability Division, NIST);T. Nguyen (Materials and Construction Research Division,NIST); S. Magonov (Veeco/Digital Instruments)

This year, we demonstrated the fabrication and useof a reference substrate that combines patterning of aself-assembled monolayer (SAM) with a surface energygradient. Our gradient micropattern (∇µp) specimensincorporate a series of micron-scale lines that continuouslychange in their surface energy compared to a constantmatrix. Patterning is achieved via a new vapor-mediatedsoft lithography of a hydrophobic chlorosilane SAM onSiO2 (matrix). A subsequent graded UV-Ozone exposuregradually changes the chemistry of the patterned SAMalong the specimen from hydrophobic to hydrophilicspecies. As shown in Figure 1, the specimen designincludes two calibration fields, which reflect the changingchemistry of the SAM lines and the constant chemistry

15

Nanometrology

Nanotube Processing and Characterization

Single-wall carbon nanotubes (SWNTs) exhibitremarkable physical properties, and there isconsiderable interest in using them as nanoscalebuilding blocks for a new generation ofapplications. Despite this promise, fundamentalissues related to the dispersion, fractionation,orientation, and manipulation of individualsingle-walled carbon nanotubes remain unresolved,and efficient bulk processing schemes do not exist.We are working at the scientific front of this rapidlyemerging field to establish research protocols thatwill help ensure that this new technology progressesas quickly and efficiently as possible, but withuniformly high standards.

Barry J. Bauer, Kalman Migler, and Erik K. Hobbie

Upon their discovery in 1991, carbon nanotubeswere recognized as ideal materials for nanotechnology

applications. Properties of carbon nanotubes differvastly depending on their diameter and chirality, andinterest in these materials stems from their extraordinarycombination of properties: superior thermal conductivity,electrical conductivity, and mechanical strength.Nanotubes are thus attracting great attention foremerging technologies such as bio-chemical sensors,next generation displays, and nano-electronics.Regardless of the ultimate applications, nanotubesclearly represent the most important new class ofmaterials in the past 15 years.

However, application development is plagued byinconsistent sample quality, compounded by a lack ofconsensus on material characterization methods and by

poor measurement reproducibility. The qualityproblems plaguing the nanotube community weredescribed in a recent news article in Nature whichstated, “the situation will not improve until an externalbody introduces standards that suppliers can follow.”Few people were surprised by the conclusion of therecent workshop: NIST must take the lead in aquantitative nanotube metrology that will allowsuppliers and customers to develop standards forthe developing industry.

The Nanotube Processing and CharacterizationProject within the Polymers Division is actively engagedin this effort. As a starting point, we are currently usingsmall-angle neutron scattering (SANS) to quantify thedegree of SWNT dispersion using a variety of dispersionchemistries (Figure 1) and, in doing so, have identifiedDNA wrapping as desirable for the purpose of fractionatingSWNTs by length, diameter, chirality, and band structure.

Figure 2: Refractive index and viscosity as a function of elutiontime in a size-exclusion chromatograph from DNA wrappedSWNTs, showing clear separation by length.

Figure 1: Measured SANS profiles obtained for two differentSWNT dispersion chemistries, showing how DNA wrappingprovides superior dispersion to other methods, such as chemicalfunctionalization.

Taking this one step further, we have begun usingsize-exclusion and ion-exchange chromatography to sortSWNTs by length and chirality (Figure 2). Followingthe protocol pioneered by DuPont researchers, we areproducing ultra clean SWNT fractions that will becharacterized with a broad suite of NIST metrologies.These results will in turn be used to establish universalscientific standards for SWNT purity and dispersion.


W. Blair (Polymers Division, NIST); A. HightWalker (Optical Technology Division, NIST);T. Yildirim (NIST Center for Neutron Research);M. Pasquali (Rice University); M. Zheng (DuPont)

16

Combinatorial Adhesion and Mechanical Properties

Traditional methods for evaluating the engineeringproperties of polymers are time-consuming andinherently single specimen tests. Current marketdrivers increasingly demand rapid measurementplatforms in order to keep pace with competitionin the global marketplace. In this project, we aredelivering innovative combinatorial and high-throughput (C&HT) tools for the physical testingof materials, built around measurement platforms inthe NIST Combinatorial Methods Center (NCMC).

Christopher M. Stafford

Our current C&HT efforts in this project areconcentrated in two main areas: buckling mechanics

for thin film mechanical measurements and adhesiontesting platforms for probing interfacial adhesion andfracture. Here, we highlight: (1) the inversion of ourbuckling-based metrology to study the mechanicalresponse of soft polymer gels, (2) the application offinite element analysis to study buckling in multilayergeometries, and (3) the implementation of ourcombinatorial edge delamination test to study theinterfacial adhesion strength of epoxy films.

of our buckling-based technique is that a “modulus map”can be constructed by measuring the buckling wavelengthas a function of spatial position.

Figure 1: Elastic modulus of model PDMS gels measured viabuckling (■ — gradient modulus specimen, ▲ — single specimens)and via tensile test (● ).

In addition to our experimental efforts, we are alsoutilizing finite element analysis (FEA) to help guideexperimental design in our buckling-based metrologyby verifying the validity of available analytical solutionswhen applied to more complex specimen geometries.For example, we examine a composite film consistingof a soft layer confined between two stiff layers. InFigure 2, FEA reveals a critical modulus ratio belowwhich shear deformation becomes significant, thus thestandard analytical solution can no longer be appliedto measurements in this regime.

As part of the NCMC, we have launched a FocusProject aimed at developing a C&HT measurementplatform for testing interfacial adhesion and fracture inthermally cured epoxy materials. This method is basedon the modified edge-liftoff test.[2] In this Focus Project,we are building capabilities to evaluate the governingparameters for interfacial delamination and reliabilityby fabricating suitable gradient libraries in composition,thickness, temperature, and applied stress. Industrialsponsors for this Focus Project are ICI National Starchand Intel Corporation.

1. C.M. Stafford, et al. Nature Materials 3, 545 (2004).2. M.Y.M. Chiang, et al. Thin Solid Films 476, 379 (2005).


M.Y.M. Chiang, S. Guo, J.H. Kim, E.A. Wilder,W. Zhang (Polymers Division, NIST); Daisuke Kawaguchi(Nagoya University); Gareth Royston (University ofSheffield)

Figure 2: Normalized wavelength versus modulus ratio of atri-layer thin film. E2 and E1 are the moduli of the soft and stifflayer, respectively. The solid line is the analytical solution.

Nanometrology

This year, we applied our buckling-based metrology[1]

to measure the elastic modulus of soft-polymer gels. Elasticmodulus is an important design criterion in soft polymergels for biomedical applications since it impacts criticalproperties such as adhesion, swelling, and cell proliferationand growth. Leveraging our C&HT buckling-basedmetrology, we can rapidly assess the elastic modulus ofpolymer gels by inverting the experimental design: thebuckling of a sensor film of known modulus and thicknessreports the elastic modulus of the substrate, Es. Figure 1illustrates the accuracy of our approach as compared totraditional tensile tests on the same material. One advantage

17

Soft Nanomanufacturing

assembly applications, image analysis was replaced byembedded electronic sensors that detect the presence ofa particle and its size (Figure 1). This electronic signalactivates a valve to isolate a set of particles. Electronicdetection is further advantageous because it is readilyscalable to smaller particles. In comparison to previoussystems, the valves we have developed are alsoadvantageous, since they are not limited to shallowchannel profiles.

Figure 1: Inline particle characterization and counting. In theimage, a polystyrene particle is seen passing electrodes (dark).At right is shown a bimodal size distribution of liquid dropsproduced at a T-junction upstream.

Figure 2: Tubular structures (right) arise from the simulatedorganization of triangular arrangements of dipole particles,shown schematically at left.

High-throughput sensing and processing methodsrequire precision flow design and control, such as wedemonstrated and reported previously by a microfluidicanalog of the four-roll mill. Advancing beyond, wedeveloped a framework for generating chaotic flowin microchannels (described in a separate highlight).

Theoretical simulations probe the organization ofgeometrically and electrostatically asymmetric targetparticle arrangements (Figure 2). These demonstratethe relationship between particle symmetry andorganized structure. Depending on this symmetry,the assemblies exhibit filaments, sheets, tubes andicosahedra. Whereas ordinary phase separationis driven by attractive and repulsive interactions,self-assembly of more complex and finite-sizedstructures requires directional interactions.

Of consequence for sensor applications, organizationkinetics were also investigated. In particular, nucleatingagents were found to control the kinetics of assemblyand, in polymorphic systems, to specify uniquestructure.


F. Phelan, Jr., J. Douglas, K. Migler, H. Hu, P. Stone,J. Taboas, K. VanWorkum (Polymers Division, NIST);Y. Dar, S. Gibbon (ICI/National Starch); M. McDonald(Procter & Gamble); D. Discher, V. Percec (Universityof Pennsylvania); R. Tuan (NIH)

Nanomanufacturing is widely noted as a centralchallenge of nanotechnology. In the realm of softmaterials and suspended particles, it is necessaryto design particle interactions, manipulateself-assembly processes, and measure what isproduced. Guided by theoretical simulations,we are therefore developing high-throughputmicrofluidic methods for particle characterization,processing, assembly, and on-chip quality control.

Steven D. Hudson

The intricacy of biological systems inspires thedesign of artificial systems that also function

through dynamic self-assembly and in-situ monitoringand self-correction.

Our industrial partners identified measurement ofinterfacial tension as a first hurdle for high-throughputmicrofluidic fluids analysis. Particle processing andassembly methods represent the next hurdle. In thisproject, high-throughput tools are developed forthese purposes, and theoretical simulations identifyparticle arrangements whose dynamic assembly anddisassembly is promising for sensor applications.

High-throughput measurement of drop shapeby image analysis represents the cornerstone of aninstrument, developed in collaboration with industrialsponsors, that determines interfacial tension betweenfluids. The measurement principle is simple androbust — drops are stretched by known viscousforces as they traverse a constriction in the channel.The computer controlled system tracks drop positionand deformation more than one hundred times a second.

However, systems that count, isolate, and direct theassembly of particles must operate more efficiently toenable internal feedback mechanisms. Therefore, for

Nanometrology

18

Defects in Polymer Nanostructures

Nanostructured materials create new and uniquefunctionality through the accurate placement,precise shaping, and chemical modification ofnanometer scale patterns. Such materials are tobe the basis of a wide range of emerging nano-technologies that span optics, data storage, andbiomembranes. In each of these applications,defects in pattern placement, shape, and chemicalcomposition can compromise device functionality.The rapid development of these technologiesis currently offset by a lack of quantitativecharacterizations of critical defects. We haveinitiated this project to develop metrologies forcharacterizing critical defects, such as loss oflong-range order, in nanostructured materials.

Ronald L. Jones and Alamgir Karim

The optical, magnetic, and electronic properties ofa film or surface are dramatically changed by the

inclusion and placement of nanometer-scale patterns.The capability to adjust material properties in thismanner is central to the development of sub-wavelengthoptics, high selectivity biomembranes, nanoparticlesynthesis, and ultrahigh capacity data storage. In eachof these applications, variations in pattern shape andplacement can drastically alter functionality and deviceviability.

Fabrication of nanostructured surfaces is performedthrough a wide range of patterning platforms. Whilephotolithographic techniques are traditional routestoward precise patterning, the high cost and complexityof patterning at nanometer length scales has spawneda variety of alternative techniques such as nanoimprintlithography (NIL), self-assembly, and templatedself-assembly. Each fabrication technique strivesagainst a common set of critical defects such asvariation in pattern placement, chemical uniformityacross the pattern cross section, and precision inpattern shape.

To address the needs of this emerging technologicalarea, we have initiated a new program to developmetrologies for long-range order, a critical parameterin optical and data storage applications. Currently,long-range order is quantified from Fourier transformsof real-space microscopy images. However, thedisparity in the pattern length scale (~ 10 nm) and thelength scale of ordering (~ 100 µm) challenges themeasurement range of existing techniques based onscanning electron and scanning probe microscopies.Visible light probes are often complicated by complexinteractions with nanometer scale features.

Using small angle x-ray scattering (SAXS), we aredeveloping quantitative descriptions of long-rangeorder, grain size, and pattern shape in hexagonallyarrayed cylinders produced on silicon substrates usingboth nanoimprint lithography (NIL) and self-assembledblock copolymers (BCP).

Figure 1: Scanning electronmicroscopy image showinga regular array of hexagonallypacked columns formed insilicon oxide.

Figure 2: SAXS data from arrays of hexagonally packedcolumns formed by NIL (left) and self assembly (right).

For each method of pattern formation, long-rangeorder results in a characteristic diffraction pattern.However, the occurrence of a hexagonal diffraction patternfrom the NIL pattern indicates a single crystal spanningthe entire 150 x 150 µm beam spot, while the BCP filmconsists of multiple, randomly oriented crystals. In bothcases, systematic errors in the placement of the patternson the lattice create a characteristic decay in the intensityas a function of the distance from the beam center.

In addition to developing metrologies for long-rangeorder, we continue to develop a suite of metrologies thataddress critical needs in a wide range of nanostructuredmaterials applications. These include nanostructuredsurfaces for adhesion and wettability, as well asnanostructured materials designed for uniqueelectro-optical and magnetic properties.


J.F. Douglas (Polymers Division, NIST);S. Satija (NIST Center for Neutron Research);R. Briber (University of Maryland); H.-C. Kim (IBM)

Nanometrology

19

Critical Dimension Small Angle X-Ray Scattering

The feature size in microelectronic circuitry isever decreasing and now approaches the scaleof nanometers. This creates a need for newmetrologies capable of non-destructivemeasurements of small features with sub-nmprecision. NIST has led the effort in developingsmall angle x-ray scattering to address this need.This x-ray based metrology has been included inthe ITRS roadmap as a potential metrologicalsolution for future generation microelectronicsfabrication. Other applications of thistechnique in areas such as nano-rheologyand nanofabrication are being explored.

Wen-li Wu and Ronald L. Jones

The demand for increasing computer speed anddecreasing power consumption continues to shrink

the dimensions of individual circuitry componentstoward the scale of nanometers. When the smallest,or “critical”, dimensions are < 40 nm, the acceptabletolerance will be < 1 nm. This creates significantchallenges for measurements based on electronmicroscopy and light scatterometry. Device viabilityalso requires the measurement be non-destructive.In addition, the continuing development of new materialsfor extreme ultraviolet photoresists, nanoporous low-kdielectrics, and metallic interconnects all requirehigh-precision dimensional measurements for processdevelopment and optimization.

To address industrial needs, we are developing ahigh-precision x-ray based metrology termed CriticalDimension Small Angle X-ray Scattering (CD-SAXS).This technique is capable of non-destructivemeasurements of test patterns routinely used bymicroelectronic industries to monitor their fabricationprocess. A collimated monochromatic x-ray beamof sub-Å wavelength is used to measure the patterndimensions on a substrate in transmission mode.CD-SAXS has previously demonstrated a capabilityfor sub-nm precision for periodicity and line widthmeasurements.

This year, we have extended the capabilities toprovide more detailed quantifications of the patterncross section. This includes both basic dimensions,such as pattern height and sidewall angle, as well as thedepth profile of the sidewall damage of nano-patternedlow-k dielectrics. The capability to provide basicdimensions is complementary to existing analysesprovided by SEM, however CD-SAXS offers significantadvantages in its non-destructive capability. In contrastto visible light scatterometry, detailed information on

refractive indices and composition of the pattern are notrequired for data reduction. These capabilities and theability to measure patterns approaching dimensions of10 nm have led to the inclusion of CD-SAXS on theInternational Technology Roadmap for Semiconductors(ITRS) as a potential metrology for the 45 nmtechnology node and beyond.

So far, all CD-SAXS measurements have beencarried out at the Advanced Photon Source ofArgonne National Laboratory. As an important stepin demonstrating the potential of technology transfer,we are constructing the world’s first laboratorybased CD-SAXS instrument. When completed, thisinstrument will serve as a prototype for lab-based tooldevelopment as well as a world-class metrology toolfor nanotechnology research.

Future efforts will develop capabilities forquantifying defects and features with complex shapessuch as vias or contact holes. In addition, we willcontinue to expand efforts in supporting othernanofabrication technologies such as those basedon nanoimprint and self assembly.


C. Soles, H. Lee, H. Ro, E. Lin (Polymers Division,NIST); K. Choi (Intel); D. Casa, S. Weigand, D. Keane(Argonne National Laboratory); Q. Lin (IBM)

Figure 1: Diffraction patterns collected over a range of samplerotation angles. The distance between the pronounced horizontalridges provides the sidewall angles β, while the relative intensityand placement of the other diffraction spots provide periodicity,line width, and line height. [qx = 4 π sin(θ /2)/λ, where θ is theangle relative to the diffraction axis and λ is the wavelength ofthe radiation.]

Nanometrology

20

Nanoimprint Lithography

Nanoimprint lithography (NIL) is emerging asa viable next generation lithography with highthroughput and a patterning resolution better than10 nm. However, wide-spread availability of suchsmall nanoscale patterns introduces new metrologychallenges as the ability to pattern now surpassesthe capability to measure, quantify, or evaluate thematerial properties in these nanoscale features.We develop high-resolution metrologies to augmentand advance NIL technology, with current focuson characterizing shape and the fidelity ofpattern transfer.

Christopher L. Soles and Ronald L. Jones

Nanoimprint lithography (NIL) is a conceptuallysimple process whereby nanoscale patterns are

written once into a master, typically Si, quartz, or someother hard material, using a high resolution but slowpatterning technology such as e-beam lithography.This master can be rapidly and repeatedly replicatedby stamping it into a softer resist film. This imprintreplication technique is a cost-effective way to combinethe high-resolution patterning of e-beam lithographywith the high throughput of a stamping process.

cross-section (height, width, side-wall angle) withnm resolution. Likewise, specular x-ray reflectivity(SXR) was introduced to quantify the patterncross-section and the residual layer thickness with nmresolution. In turn, these accurate shape metrologiesenable quantitative studies of imprint resolution andthe stability of nanoscale imprinted patterns.

Using CD-SAXS, we demonstrated the fidelity ofpattern transfer concept. The pattern cross-sectionsin the master and the imprint were independentlycharacterized and then compared, to quantify how wellthe resist material fills and replicates the features ofthe master. Varying the imprint temperature, pressure,time, and the molecular mass of the imprint materialimpacts the fidelity of pattern transfer process. Wealso tracked the in-situ evolution of the cross-sectionwhile the patterns were annealed close to their glasstransition. Rather than a viscous decay, the patternsdecreased in height much faster than they broadened inwidth, owing to the residual stresses in the structuresinduced by the imprinting procedure. These residualstresses appear to increase with molecular mass, leadingto faster rates of pattern decay in higher molecular massresists.

NIL holds great promise in semiconductorfabrication. The high resolution and low cost ofownership make NIL attractive in comparison toexpensive next-generation optical lithography tools.However, over the past few years, the interest in NILhas dramatically expanded beyond the realm oftraditional CMOS applications. NIL-based solutionsare being implemented for optical communications,memory, displays, and biotechnology. Because of theseemerging niche applications, NIL is quickly becominga widely used and versatile nanofabrication tool.

Our objective is to develop metrologies that arecrucial to advancing NIL as an industrially viablepatterning technology. Initial efforts have focused ondeveloping and applying very accurate pattern-shapemeasurements. Critical dimension small angle x-rayscattering (CD-SAXS) is a transmission x-ray scatteringtechnique that can quantify the pattern pitch and

SXR was used to quantify the residual layerthickness, pattern height, and the relative line shapecross-section. The residual layer is the thin layer ofresist that the master is unable to fully displace as it ispressed into the resist film. Precise knowledge of theresidual thickness is critical for subsequent etchingprocesses. The key to this measurement is that thex-rays average density over length scales larger thanthe sub-µm dimensions of the patterns. This leads tothe bilayer equivalency model shown above where thepatterns can be modeled as a uniform layer of reduceddensity to extract pattern height and residual layerthickness with nm precision. Like CD-SAXS, SXRquantitatively compares the imprint and the mold toevaluate the fidelity of pattern transfer.


H.W. Ro, H.-J. Lee, A. Karim, E.K. Lin, J.F. Douglas,W. Wu (Polymers Division, NIST); S.W. Pang(University of Michigan); D.R. Hines (University ofMaryland); C.G. Willson (University of Texas–Austin);L. Koecher (Nanonex); D. Resnick (MolecularImprints)

Nanometrology

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Program Overview

Materials for Electronics

The U.S. electronics industry faces stronginternational competition in the manufacture of smaller,faster, more functional, and more reliable products.Many critical challenges facing the industry requirethe continual development of advanced materialsand processes. The NIST Materials Science andEngineering Laboratory (MSEL) works closely withU.S. industry, covering a broad spectrum of sectorsincluding semiconductor manufacturing, devicecomponents, packaging, data storage, and assembly,as well as complementary and emerging areas such asoptoelectronics and organic electronics. MSEL has amultidivisional approach, committed to addressing themost critical materials measurement and standardsissues for electronic materials. Our vision is to bethe key resource within the Federal Government formaterials metrology development and will be realizedthrough the following objectives:■ Develop and deliver standard measurements and data

for thin film and nanoscale structures;■ Develop advanced measurement methods needed by

industry to address new problems that arise with thedevelopment of new materials;

■ Develop and apply in situ as well as real-time, factoryfloor measurements for materials and devices havingmicrometer to nanometer scale dimensions;

■ Develop combinatorial material methodologies forthe rapid optimization of industrially importantelectronic and photonic materials;

■ Provide fundamental understanding of the divergenceof thin film and nanoscale material properties fromtheir bulk values;

■ Provide fundamental understanding, including firstprinciples modeling, of materials needed for futurenanoelectronic devices.

The NIST/MSEL program consists of projects ledby the Metallurgy, Polymers, Materials Reliability, andCeramics Divisions. These projects are conducted incollaboration with partners from industrial consortia(e.g., SEMATECH), individual companies, academia,and other government agencies. The program isstrongly coupled with other microelectronics programswithin the government such as the National SemiconductorMetrology Program (NSMP). Materials metrologyneeds are also identified through the InternationalTechnology Roadmap for Semiconductors (ITRS), theInternational Packaging Consortium (IPC) Roadmap,the IPC Lead-free Solder Roadmap, the NationalElectronics Manufacturing Initiative (NEMI) Roadmap,the Optoelectronics Industry Development Association(OIDA) Roadmap, and the National Magnetic DataStorage Industry Consortium (NSIC) Roadmap.

MSEL researchers from each division have madesubstantial contributions to the most pressing technicalchallenges facing industry, from new fabricationmethods and advanced materials in the semiconductorindustry, to low-cost organic electronics, and to novelclasses of electronic ceramics. Below are just a fewexamples of MSEL contributions over the past year.

Advanced Gate DielectricsTo enable further device scaling, the capacitive

equivalent thickness (CET) of the gate stack thicknessmust be 0.5 nm to 1.0 nm. This is not achievable withexisting SiO2/polcrystalline Si gate stacks. High dielectricconstant gate insulators are needed to replace SiO2, andmetal gate electrodes are needed to replace polycrystallineSi. Given the large number of possible materials choicesfor the gate dielectric/substrate and gate dielectric/metalgate electrode interfaces, the MSEL Ceramics Divisionis establishing a dedicated combinatorial film depositionfacility to study the complex interfacial interactions.This same methodology is applicable to a wide varietyof problems in the electronic materials field.

Advanced LithographyLithography is the key enabling technology for the

fabrication of advanced integrated circuits. As featuresizes decrease to sub-65 nm length scales, challenges arisebecause the image resolution and the thickness of theimaging layer approach the dimensions of the polymersused in the photoresist film. Unique high-spatialresolution measurements are developed to identify thelimits of materials and processes for the developmentof photoresists for next-generation lithography.

Advanced MetallizationAs the dimensions of copper metallization

interconnects on microelectronic chips decrease below100 nm, control of electrical resistivity becomes critical.The MSEL Metallurgy Division is developing seedlessdeposition methods that will simplify thin-film processingand result in film growth modes that increase trenchfilling, thus lowering interconnect resistivity.

Mechanical Reliability of MicrochipsOne of the important ITRS challenges is to achieve

effective control of the failure mechanisms affectingchip reliability. Detection and characterization methodsfor dimensionally constrained materials will be critical tothe attainment of this objective. Scientists in the MSELMaterials Reliability Division are addressing this issue byfocusing on electrical methods capable of determiningthe thermal fatigue lifetime and mechanical strength ofpatterned metal film interconnects essential to microchips.

Contact: Eric K. Lin

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Polymer Photoresists for Nanolithography

Photolithography, the process used to fabricateintegrated circuits, is the key enabler and driverfor the microelectronics industry. As lithographicfeature sizes decrease to the sub 65 nm lengthscale, challenges arise because both the imageresolution and the thickness of the imaginglayer approach the macromolecular dimensionscharacteristic of the polymers used in thephotoresist film. Unique high-spatial resolutionmeasurements are developed to reveal limitson materials and processes that challenge thedevelopment of photoresists for next-generationsub 65 nm lithography.

Vivek M. Prabhu

Photolithography is the driving technology used bythe microelectronics industry to fabricate integrated

circuits with ever decreasing sizes. In addition, thisfabrication technology is rapidly being adopted inemerging areas in optoelectronics and biotechnologyrequiring the rapid manufacture of nanoscale structures.In this process, a designed pattern is transferred to thesilicon substrate by altering the solubility of areas ofa polymer-based photoresist thin film through anacid-catalyzed deprotection reaction after exposureto radiation through a mask (Figure 1). To fabricatesmaller features, next-generation photolithographywill be processed with shorter wavelengths of lightrequiring photoresist films less than 100 nm thick anddimensional control to within 2 nm.

To advance this key fabrication technology,we work closely with industrial collaborators todevelop and apply high-spatial resolution andchemically specific measurements to understandchanges in material properties, interfacial behavior,and process kinetics that can significantly affect thepatterning process at nanometer scales.

This year, we initiated two new collaborations.With SEMATECH, we are determining the materialssources of line-edge roughness in model 193-nmphotoresists. With the Intel Corporation, we areinvestigating the effect of extreme ultraviolet (EUV)exposure on pattern resolution of model EUVphotoresist materials. With these partners, we continueto provide new insight and detail into the complexphysico–chemical processes used in advancedchemically amplified photoresists. These methodsinclude x-ray and neutron reflectivity (XR, NR), smallangle neutron scattering (SANS), near-edge x-rayabsorption fine structure (NEXAFS) spectroscopy,combinatorial methods, solid state nuclear magnetic

Photoresists are multi-component mixtures thatrequire dispersion of additives, controlled transportproperties during the interface formation, and controlleddissolution behavior. The fidelity of pattern formationrelies on the materials characteristics. We examine theinfluence of copolymer compositions, molecular mass,and photoacid generator additive size to determinethe root causes of image quality by highlightingthe fundamental polymer physics and chemistry.In addition, our collaborators test our hypothesesusing 193-nm and EUV lithographic production tools.

Accomplishments for this past year include:quantification of the developer profile in ultrathin films byNR and QCM; quantification of the deprotection reactionkinetics and photoacid-reaction diffusion deprotectionfront for resolution and roughness fundamentals bycombined NR and FTIR; photoacid generator miscibilityand dispersion in complex photoresist co- and ter-polymersby NMR; and aqueous immersion dependence onphotoresist component leeching by NEXAFS.


B. Vogt, A. Rao, S. Kang, D. VanderHart, W. Wu,E. Lin (Polymers Division, NIST); D. Fischer,S. Sambasivan (Ceramics Division, NIST); S. Satija (NISTCenter for Neutron Research); K. Turnquest (Sematech);K-W. Choi (Intel); D. Goldfarb (IBM T.J. WatsonResearch Ctr); H. Ito, R. Allen (IBM Almaden ResearchCtr); R. Dammel, F. Houlihan (AZ Electronics);J. Sounik, M. Sheehan (DuPont Elect. Polymers)

Figure 1: Key lithographic process steps; each step requires aninterdisciplinary array of experimental techniques to measure thepolymer chemistry and physics in thin films. A model 193-nmresist under investigation is shown with the acid-catalyzeddeprotection reaction.

resonance (NMR)/spectroscopy, quartz crystalmicrobalance (QCM), Fourier transform infraredspectroscopy (FTIR), fluorescence correlationspectroscopy (FCS), and atomic force microscopy (AFM).


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Organic Electronics

Organic electronics has dramatically emerged inrecent years as an increasingly important technologyencompassing a wide array of devices andapplications including embedded passive devices,flexible displays, and sensors. Device performance,stability, and function critically depend upon chargetransport and material interaction at the interfacesof disparate materials. We develop and applynondestructive measurement methods to characterizethe electronic and interfacial structure of organicelectronics materials with respect to processingmethods, processing variables, and materialscharacteristics.

Eric K. Lin and Dean M. DeLongchamp

Organic electronic devices are projected torevolutionize new types of integrated circuits

through new applications that take advantage of low-cost,high-volume manufacturing, nontraditional substrates,and designed functionality. The current state of organicelectronics is slowed by the concurrent developmentof multiple material platforms and processes and a lackof measurement standardization between laboratories.A critical need exists for new diagnostic probes, tools,and methods to address these technological challenges.

Organic field effect transistor test structures werealso designed and fabricated onto silicon wafers withvariations in transistor channel length and width. Devicesconstructed using organic semiconductors such aspoly(3-hexyl thiophene) (P3HT) were tested for theirelectrical characteristics such as the field effect holemobility, on/off ratios, and threshold mobilities. Variationsin mobility, for example, are observed with changes inprocessing variables such as annealing temperature andcasting solvent. Correlations are found between deviceperformance and the microstructure of P3HT as quantifiedby NEXAFS, optical ellipsometry, and FTIR spectroscopy.


J. Obrzut, B. Vogel, C. Chiang, K. Kano, C. Brooks,N. Fisher, B. Vogt, H. Lee, Y. Jung, W. Wu (PolymersDivision, NIST); S. Sambasivan, D. Fischer (CeramicsDivision, NIST); M. Gurau, L. Richter (ChemicalScience and Technology Laboratory, NIST); C. Richter,O. Kirillov (Electronics and Electrical EngineeringLaboratory, NIST); R. Crosswell (Motorola);L. Moro, N. Rutherford (Vitex); A. Murphy,J.M.J. Frechet, P. Chang, V. Subramanian (Universityof California–Berkeley); M. Ling, Z. Bao (StanfordUniversity); M. Chabinyc, Y. Wu, B. Ong (Xerox)

Figure 1: Schematic of the geometry of near-edge x-ray absorptionfine structure (NEXAFS) spectroscopy for the determination ofthe orientation of an oligothiophene organic semiconductorsynthesized by the University of California–Berkeley.

Organic electronics presents different measurementchallenges from those identified for inorganic devices.We are developing an integrated suite of metrologies tocorrelate device performance with the structure, properties,and chemistry of materials and interfaces. We applynew measurement methods to provide the data andinsight needed for the rational and directed developmentof emerging materials and processes. Studies includeAC measurements of organic semiconductor thin films,

Figure 2: Schematic of an organic field effect transistor (OFET)and a photo of the NIST OFET test bed fabricated onto silicon.

the influence of surface modification layers on deviceperformance, and the evaluation of moisture barrierlayers for device encapsulation.

This year, near-edge x-ray absorption fine structure(NEXAFS) spectroscopy was applied to several classesof organic electronics materials to investigate theelectronic structure, chemistry, and orientation ofthese molecules near a supporting substrate. NEXAFSspectroscopy was used successfully to quantify thesimultaneous chemical conversion, molecular ordering,and defect formation of soluble oligothiopheneprecursor films for application in organic field effecttransistors. Variations in field-effect hole mobilitywith thermal processing were directly correlated tothe orientation and distribution of molecules within3 nm to 20 nm thick films.


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Nanoporous Low-k Dielectric Constant Thin Films

NIST provides the semiconductor industry withunique on-wafer measurements of the physicaland structural properties of nanoporous thin films.Several complementary experimental techniques areused to measure the pore and matrix morphology ofcandidate materials. The data are used by industryto select candidate low-k materials. Measurementmethods such as x-ray porosimetry and smallangle x-ray scattering are developed that may betransferred to industrial laboratories. Methods arebeing developed to measure patterned low-k samplesand to assess the extent of structure modificationcaused by plasma etch.

Eric K. Lin and Wen-li Wu

Future generations of integrated circuits will requireporous low-k interlayer dielectric materials to

address issues with power consumption, signalpropagation delays, and crosstalk that decrease deviceperformance. The introduction of nanometer scalepores into a solid film lowers its effective dielectricconstant. However, increasing porosity adverselyaffects other important quantities such as the physicalstrength needed to survive chemical mechanicalpolishing steps and barrier properties to contaminantssuch as water. These effects pose severe challengesto the integration of porous dielectrics into thedevice structure.

There is a need for nondestructive, on-wafercharacterization of nanoporous thin films. Parameterssuch as the pore size distribution, wall density, porosity,film uniformity, elemental composition, coefficientof thermal expansion, and film density are needed toevaluate candidate low-k materials. NIST continuesto develop low-k characterization methods using acombination of complementary measurement methodsincluding small angle neutron and x-ray scattering(SANS, SAXS), high-resolution x-ray reflectivity (XR),x-ray porosimetry (XRP), SANS porosimetry, and ionscattering. To facilitate the transfer of measurementexpertise, a recommended practice guide for XRP isavailable for interested researchers.

In collaboration with industrial and universitypartners, we have applied existing methods to newlow-k materials and developed new methods to addressupcoming integration challenges. A materials databasedeveloped in collaboration with SEMATECH is usedextensively by SEMATECH and its member companiesto help select candidate materials and to optimizeintegration processing conditions. We address theeffects of the ashing/plasma etch process on the low-k

material during pattern transfer. Often surfacesexposed to ashing/plasma densify and lose terminalgroups (hydrogen or organic moiety) resulting in anincreased moisture adsorption and thus dielectricconstant. XR measurements enable quantificationof the surface densification or pore collapse inashing-treated and/or plasma-treated blanket films.

Figure 1: Four models of the damage layer profile plotted asscattering length density (SLD) as a function of position within aline. The matrix has a relative SLD of zero in the above plots.

This year, a new method using SAXS wasdeveloped to investigate the effect of plasma etch onpatterned low-k films. After the plasma etch process,samples are backfilled with the initial low-k material.Any densification of the sidewall may be observable byx-ray scattering from the cross-section of a patternednanostructure. This SAXS work was carried out atArgonne National Laboratory using line gratings oflow-k material. The resulting data can then becompared with several different scattering modelsfor the densification of the patterned low-k materialas shown in Figure 1. Distinctions between modelssuch as these will significantly help semiconductormanufacturers to accelerate the integration of low-kmaterials into next generation devices.


H. Lee, C. Soles, R. Jones, H. Ro, D. Liu, B. Vogt(Polymers Division, NIST); C. Glinka (NIST Centerfor Neutron Research); Y. Liu (SEMATECH); Q. Lin,A. Grill, H. Kim (IBM); J. Quintana, D. Casa (ArgonneNational Laboratory); K. Char, D. Yoon (Seoul NationalUniversity); J. Watkins (University of Massachusetts)


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Program Overview

Advanced Manufacturing Processes

The competitiveness of U.S. manufacturers dependssubstantially on their ability to create new product conceptsand to quickly translate such concepts into manufacturedproducts that meet their customers’ increasing expectationsof performance, cost, and reliability. This is equally truefor well-established “commodity” industries, such asautomotive, aerospace, and electronics; for materialssuppliers of aluminum, steel, and polymers; and forrapidly growing industries based on nanotechnologyand biotechnology. In support of these industries,MSEL is developing robust measurement methods,standards, software, and process and materials dataneeded for design, monitoring, and control of newand existing materials and their manufacturing processes.The Advanced Manufacturing Processes Program focuseson the following high-impact areas:

■ Development of combinatorial and high-throughputmethods for developing and characterizing materialsranging from thin films and nanocomposites to microand macroscale materials structures;

■ Automotive industry-targeted R&D for improvedmeasurement methods for sheet metal formingof lightweight metals and for the developmentof hydrogen storage materials needed forhydrogen-powered vehicles;

■ Development of innovative, physics-based processmodeling tools for simulating phase transformationsand deformation during manufacturing and creationof the databases that support such simulations;

■ National traceable standards having a major impacton trade, such as hardness standards for metals andMALDI process standards for polymers; and

■ Development of innovative microfluidic testbedsfor process design and characterization of polymerformulations.

Our research is conducted in close collaborationwith industrial partners, including industrial consortia,and with national standards organizations. Thesecollaborations not only ensure the relevance of ourresearch, but also promote rapid transfer and utilizationof our research by our partners. Three projects from theAdvanced Manufacturing Methods Program arehighlighted below.

NIST Combinatorial Methods Center (NCMC)

The NCMC develops innovative combinatorial andhigh-throughput (C&HT) measurement techniques andexperimental strategies for accelerating the discoveryand optimization of complex materials and products,such as polymer coatings and films, structural plastics,

fuels, personal care goods, and adhesives. TheseC&HT array and gradient methods enable the rapidacquisition and analysis of physical and chemicaldata from materials libraries, thereby acceleratingmaterials discovery, manufacturing design, andknowledge generation. In 2005, the NCMCConsortium consisted of 19 institutions from industry,government laboratories, and academic groups, whichrepresents a broad cross-section of the chemical andmaterials research sectors. A growing component ofthe NIST NCMC program is focused on acceleratingthe development and understanding of emergingtechnologies, including nanostructured materials,organic electronics, and biomaterials, and, in particular,on the nanometrology needed for C&HT-basedresearch for these technologies.

Forming of Lightweight Materials

Automotive manufacturing is a materials intensiveindustry that involves approximately 10 % of the U.S.workforce. In spite of the use of the most advanced,cost-effective technologies, this globally competitiveindustry has major productivity issues related tomaterials measurements, materials modeling, andprocess design. Chief among these is the difficultyof designing stamping dies for sheet metal forming.An ATP-sponsored workshop (“The Road Ahead,”June 20–22, 2000) identified problems in the productionof working die sets as the main obstacle to reducingthe time between accepting a new design and actualproduction of parts. This is also the largest singlecost (besides labor) in car production. Existing finiteelement models of deformation and the materialsmeasurements and data on which they are based areinadequate to the task of evaluating a die set design:they do not accurately predict the multi-axial hardening,springback, and friction of sheet metal during metalforming processes and, therefore, the stamping diesdesigned using finite element analyses must be modifiedthrough physical prototyping to produce the desiredshapes, particularly for high-strength steels andaluminum alloys. To realize the weight savings andincreased fuel economy enabled by high-strengthsteel and aluminum alloys, a whole new level offormability measurement methods, models, and datais needed for accurate die design, backed by a betterunderstanding of the physics behind metal deformation.The MSEL Metallurgy Division is working with theU.S. automakers and their suppliers to fill these needs.A key component of our program is the uniquemulti-axial deformation measurement facility withwhich local strains in deformed metal sheet can bemeasured in situ. This facility has enabled NISTto take a key role in developing new methods for

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assessing springback, residual stresses, frictionbetween the sheet metal and die during forming, andsurface roughening, and in providing benchmark datafor international round-robin experiments for finiteelement code. New techniques for detecting localdeformation events at surfaces are providing insightsinto the physics of deformation and are leading tophysics-based constitutive equations.

Hardness Standardization:Rockwell, Vickers, and Knoop

Hardness is the primary test measurement used todetermine and specify the mechanical properties ofmetal products and, as such, determines compliancewith customer specifications in the national andinternational marketplace. The MSEL MetallurgyDivision is engaged in developing and maintainingnational traceability for hardness measurements andin assisting U.S. industry in making measurementscompatible with other countries around the world,enabled through our chairing the ASTM InternationalCommittee on Indentation Hardness Testing and headingthe U.S. delegation to the ISO Committee on HardnessTesting of Metals, which oversees the developmentof the organizations’ respective hardness programs.Our specific R&D responsibilities include thestandardization of the national hardness scales,development of primary reference transfer standards,leadership in national and international standardswriting organizations, and interactions and comparisonswith U.S. laboratories and the National MetrologyInstitutes of other countries.

Contact: Michael J. Fasolka

Program Overview

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NIST Combinatorial Methods CenterPioneer and Partner in Accelerated Materials Research

Combinatorial and high-throughput (C&HT)methods hold great potential for making materialsresearch more productive, more thorough, and lesswasteful. However, significant barriers preventthe widespread adoption of these revolutionarytechniques. Through creative, cost-effectivemeasurement solutions, and with an eye towardsfruitful collaboration, the NIST CombinatorialMethods Center (NCMC) strives to ease theacquisition of C&HT techniques by the materialsresearch community.

Michael J. Fasolka

The NIST Combinatorial Methods Center is now inits fourth year of service to industry, government

laboratories, and academic groups interested in acquiringC&HT capabilities for materials research. In 2005, theNCMC consortium included 19 member institutions(see table), which represent a broad cross-section of thechemical and materials research sectors.

The NCMC fosters wide-spread adaptation ofC&HT technologies through two complementary efforts.The first is an extensive research program, centered inthe Multivariant Measurement Methods Group of the NISTPolymers Division. Our research provides innovativemeasurement solutions that serve to accelerate thediscovery and optimization of complex products suchas polymer coatings and films, structural plastics, fuels,personal care goods and adhesives. Moreover, a growingcomponent of our program aims to speed the developmentand understanding of emerging technologies includingnanostructured materials, nanometrology, organicelectronics, and biomaterials. Several of these researchdirections are highlighted elsewhere in this report,as identified by the NCMC symbol (see top right).

emerging industrial needs for C&HT measurementsof materials systems such as biomaterials and organicelectronics. Accordingly, NCMC-6 included plenarysymposia outlining engineering issues in these advancedsystems, sessions illustrating NIST capabilities in theseareas, and a panel discussion aimed at determining newmeasurements that should be pursued.

In addition, on May 2–3 2005, we hosted NCMC-7:Adhesion and Mechanical Properties II. Central tothis event was a symposium presenting new NCMCmethods for the development and optimization ofadhesives. Highlights included a new gradient peel-testfor the HT assessment of backed adhesives (e.g., tapes),and approaches for the rapid screening of epoxyformulations. A variation of our buckling technique tomeasure modulus, useful for evaluating soft systemssuch as polymer gels, was also described.


“As a member of NCMC, I believe that Procter & Gamble hasaccess to a high-performance work group with expertise in highthroughput and combinatorial techniques. The conferenceshave been particularly valuable for networking with NISTscientists as well as other industrial members of NCMC.”

— M. McDonald (Procter and Gamble)

“The coatings industry has been traditionally perceived to reactslowly to implementing newer and quantifiable measurementtechniques for characterizing structure–property relationshipsin paints and films. The [NCMC] has pioneered elegantapproaches that can significantly reduce experimental time[for] testing coating formulation performance.”

— D. Bhattacharya (Eastman Chemical)

In conjunction with its research program, theNCMC conducts an outreach effort to disseminateNIST-developed C&HT methods, assess industrymeasurement needs, and form a community to advancethe field. A key component of NCMC outreach is ourseries of member workshops. On November 8–9 2004,we hosted our 6th workshop, NCMC-6: AdvancedMaterials Forum. The goal of NCMC-6 was to gauge

“The combinatorial methods program at NIST makes the NCMCcritical to any company’s development of high-throughputworkflows. The import of this effort to industry is clearlyindicated by your center’s number of industrial members.”

— J. Dias (ExxonMobil)

Moreover, this year the NCMC continued communityforming activities by organizing several high-profilesessions dedicated to C&HT research at nationalconferences, including meetings of the American PhysicalSociety, the American Chemical Society, the MaterialsResearch Society, and the Adhesion Society.


C.M. Stafford, P.M. McGuiggan, K.L. Beers,A. Karim, E.J. Amis (Polymers Division, NIST)

NCMC Members (*New in FY2005):Hysitron International

IntelICI/National Starch & Chemicals

L’Oreal*PPG Industries

Procter & GambleRhodia

Univ. of Southern MississippiVeeco/Digital Instruments

Air Force Research LabAir Products & Chemicals Arkema Inc.BASFBayer PolymersBPDow Chemical CompanyEastman ChemicalExxonMobil ResearchHoneywell International

For more information on the NIST CombinatorialMethods Center, please visit http://www.nist.gov/combi.

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Polymer Formulations:Materials Processing and Characterization on a Chip

We develop high-throughput methods toadvance polymer formulations science throughthe fabrication of microscale instrumentationfor measuring physical properties of complexmixtures. Adaptation of microfluidic technologyto polymer fluid processing and measurementsprovides an inexpensive, versatile alternativeto the existing paradigm of combinatorialmethods. We have built a platform of polymerformulations-related functions based onmodified microfluidic device fabricationmethods established in our facilities.

Kathryn L. Beers

Microfluidic device fabrication methods previouslydeveloped in the Polymers Division enable

combinatorial fabrication and characterization ofpolymer libraries. Recent accomplishments includethe integration of multiple functions on a chip for theformulation, mixing, processing, and characterizationof polymer particles for evaluation of dental compositematerials and the fabrication of gradient polymerbrush surfaces for measuring the behavior ofstimuli-responsive surfaces.

with shrinkage. The first publication on this work(Langmuir 21, 3629, 2005) was recently profiled inthe Research Highlights of Lab on a Chip.


Figure 1: (a) A thiolene microfluidic device used to create,mix, polymerize and characterize monomer droplets.(b) Optical images of monomer droplets and polymer particles.(c) Raman spectra of monomer (red) and polymer (black).

Figure 2: (a) Schematic of amphiphilic block copolymer brushgradients representing the proposed conformation shift in responseto good and poor solvents for the top block layer. (b) Water contactangle measurements as a function of top block thickness on threegradients of top block thickness on uniform bottom blocks of threedifferent lengths (blue – 4 nm, red – 10 nm, green – 14 nm) in good(open) and poor (filled) solvents for the top block.

Building on our ability to form organic-phasedroplets in thiolene-based microfluidic devices(Figure 1a), we can establish libraries of dropletswith systematic composition variations. The dropletsare subject to various processes such as mixing andphotopolymerization on the chip. Raman spectroscopyon the chip (Figure 1c) and optical imaging (Figure 1b)are used to measure and correlate properties such asmonomer composition and conversion to polymer

Microchannel confined surface initiated polymerizationwas used to prepare surfaces with gradients of molecularmass and block and statistical copolymer composition.The block copolymer surfaces were studied for their abilityto reorganize at the air/solution interface dependingon the nature of the polymer and solvent (Figure 2a).The ability of the surface layer to rearrange was shownto depend on the thickness of both the top and bottomblock layers (Figure 2b).

The capabilities for controlled radical polymerizationon a chip (CRP Chip) were also extended this year toinclude block copolymer synthesis and higher-ordercontrol of solution compositions. A three-input devicewas developed, enabling stoichiometric variations inreactions and faster measurement of kinetic behavior(Macromol. Rapid Commun. 26, 1037, 2005).


Z.T. Cygan, C. Xu, S. Barnes, T. Wu, A.J. Bur,J.T. Cabral, S.D. Hudson, A.I. Norman, J. Pathak,W. Zhang, M.J. Fasolka, E.J. Amis (Polymers Division,NIST)

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Matrix-assisted laser desorption ionizationtime-of-flight mass spectrometry (MALDI-TOF-MS)is being developed as a method for absolutemolecular mass distribution measurement ofsynthetic polymers. This means determining acomprehensive uncertainty budget for a complexmeasurement technique that must include bothType A (“random”) and Type B (“systematic”)uncertainties.

William E. Wallace

In mass spectrometry, methods exist to calibrate the mass axis with high precision and accuracy.

In contrast, the ion-intensity axis is extremely difficultto calibrate. This leads to large uncertainties inquantifying the content of mixtures. This is even truewhen the mixture is composed solely of different massoligomers of the same chemical species as in the caseof polymer polydispersity. The aim of this project isto calibrate the ion intensity axis. This task hasbeen divided into three parts: sample preparation/ionproduction, instrument optimization/ion separation,and data analysis/peak integration. Each part isnecessary but on its own is not sufficient toguarantee quantitation.

We study the MALDI ion-creation processphenomenologically using combinatorial libraries.The ratio of analyte to matrix is varied along a linearpath laid down by nebulizing a continuously varyingmixture of two solutions, one analyte+matrix+ saltand the other matrix+salt. In our case, the analyte isa mixture of two polymers having different end groupsand closely matched molecular mass distributions.The figure on this page shows such a librarywhere the blue arrows indicate a linearly changinganalyte:matrix ratio.

To this, we add stochastic-gradient numericaloptimization to adjust the instrument parameters ateach composition to give a mass spectrum that bestmatches the known polymerA:polymerB ratio in theanalyte. Instrument parameters optimized includelaser energy, ion extraction voltage, ion lensvoltage, extraction delay time, and detector voltage.Stochastic methods must be used because the datahave some measure of Type A random uncertainty(i.e., “noise”) to them; therefore, exact values of thefunction to be optimized are not available.

Finally, to this we add our MassSpectator softwarewhich ensures unbiased, logically-consistent integration

of the peaks in the (noisy) mass spectrum. A softwarescript has been written around MassSpectator thatautomatically identifies oligomeric series in the massspectrum and calculates the total amount and themolecular mass moments for each series identified.


Quantitative Polymer Mass Spectrometry

An early embodiment of our approach can befound in ASTM Standard Test Method D7134, thefirst MALDI-TOF-MS method endorsed by ASTM.Working through the Versailles Project on AdvancedMaterials and Standards (VAMAS), and in closecooperation with our industry and national metrologyinstitute (NMI) colleagues from around the world, aninterlaboratory comparison was initiated to understandthe nexus of critical measurement factors whenperforming quantitative polymer mass spectrometry.From the knowledge gained by the interlaboratorycomparison, D7134 was written with particularattention paid toward controlling the critical factors.

The MALDI project maintains a vigorous,worldwide outreach program including an onlinepolymer MALDI recipes catalog, annual polymer MSworkshops, and the availability of our MassSpectatorsoftware on the web. For more information onany of these topics please visit our web page at:www.nist.gov/maldi.


W.R. Blair, K.M. Flynn, C.M. Guttman (PolymersDivision, NIST); A.J. Kearsley (Mathematical &Computational Sciences Division, NIST)

31

Biomaterials

Rapid development of medical technologiesdepends on the availability of adequate methods tocharacterize, standardize, control, and mass producethem. To realize this goal, a measurement infrastructureis needed to bridge the gap between the exponentiallyincreasing basic biomedical knowledge and clinicalapplications. The MSEL Biomaterials Program is acollaborative effort creating a new generation ofperformance standards and predictive tools targetingthe metrology chain for biomedical research.

Today, all areas of materials science confront realsystems and processes. In the biomaterials arena,we can no longer advance science by simply studyingideal model systems. We must comprehend complexrealistic systems in terms of their structure, function,and dynamics over the size range from nanometers tomillimeters. MSEL is uniquely positioned to make amajor contribution to the development of measurementinfrastructure through three focus areas: SystemsBiology, Bioimaging, and Nanobiosensing.

Systems BiologyMSEL research in systems biology focuses on

quantifying relationships of systems at the cell, tissue,and organ level. To meet this need, we are developinglibraries of reference materials, high-throughputtechniques for screening libraries, and informaticsapproaches for data analysis and interpretation.Physicochemical and biochemical components areorganized using patterning, phase separating, andself-assembling processes. Physicochemicalcomponents of interest include modulus and surfacetopography; biochemical components of interestinclude peptide moieties that interact specificallywith cell receptors.

Gradient libraries of tyrosine derivatizedpolycarbonate blends and fibronectin/poly(hydroethyl-methacrylate) gradients were developed as referencematerials for biomaterial research, such that cellresponses included changes in geometry, distribution,and proliferation, to assess intercellular communicationamong osteoblast and fibroblast cells. Complementingthese surface studies, we are developing metrologiesto establish the relationship between 3D scaffoldmorphology (i.e., porosity and permeability) andcell response. Studies focused on identifying therelationship between applied macroscopic stressesand local stresses at the cellular level is also underway,which will provide valuable input into developmentof finite-element models.

Experiments on the mechanical stimulationof tissues and tissue engineered constructs wereconducted to understand the role of metrologyin diagnostic testing of healthy or disease states.Stress–strain relationships were defined for vascularsmooth muscle cells and bovine cardiac tissues.Specialized bioreactors coupled to ultrasound andinfra-red spectroscopy were successful in differentiatingresponse among the systems. We have demonstratedthat the structure–property relations in healthy tissueof pulmonary arteries, and in tissue that has remodeledin response to the onset of disease, can be assessedusing mechanical testing, quantitative ultrasoniccharacterization, and histology.

BioimagingAdvances were made in developing and optimizing

physical methods and informatics tools to enhancebioimaging and visualization technologies at multiplelength scales. With the reduction of backgroundnoise, images were obtained using broadband coherentanti-stokes Raman scattering microscopy with a 10-foldincrease in signal, and proteins on the surface of polymerblends were differentiated. Optical techniques like OCMand CFM, with spatial resolutions of ≈1 µm, wereemployed to image dynamic cell culture experimentsin-situ in a bioreactor. Other advances in computationalmodeling of single cell forces and cell populations werecarried out to predict normal ossification patterns andcartilage formation. By combining information fromdifferent techniques on the same sample and visualizingstructure using interactive, immersive visualizationtechniques, scientists will gain new insights into thephysics and materials science of complex systems.

NanobiosensingResearch in this focus area concentrates on the

development of techniques to measure and manipulatebiological atoms, molecules, and macromolecules atthe nanoscale level (1–100 nm). Mechanical toolsincluding an optical trap and bioMEMS devices thatcan be integrated with currently used biologicaltechniques for evaluating and measuring cellularresponse (i.e., gene expression, cell morphology,area of adhesion) were developed. Additional studiesfocus on identifying mechanical forces that indicatethe onset of osteogenesis and angiogenesis.

Contact: Eric J. Amis

Program Overview

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Combinatorial Methods for Rapid Characterizationof Cell-Surface Interactions

The increasingly complex nature of functionalbiomaterials demands a multidisciplinaryapproach to identify and develop strategiesto both characterize and control cell-materialinteractions. A robust framework outlining theinteractions governing biomaterial performancedoes not exist but is desperately needed. Thisproject provides the basis for this frameworkby focusing on fabrication of single andmulti-variable continuous combinatorial librariesto rapidly identify compositions and physicalproperties exhibiting favorable cell-materialinteractions.

Matthew L. Becker and Lori A. Henderson

Developmental biology and tissue engineering areavenues of research that must be fully integrated

to realize the opportunities in regenerative medicine.For example, while the interactions between cell andextracellular matrix have been studied extensively, muchless is understood regarding the influence of syntheticmaterials. There is little doubt that having good control ofsurface morphology as well as advanced high-throughput(HT) metrologies for analyzing cell-surface interactionsare needed for biological interpretations, and whilechemical and topographical manipulations of surfaceshave been established, HT methods to evaluatebiological responses to these manipulations have not.For these reasons, we are developing metrologies andHT platforms to rapidly analyze physicochemical,mechanical, and material properties of biomaterials.We provide examples of two of our sample fabricationmethods, distinct from traditional self-assembledmonolayer approaches, that are being used to design,manipulate, and quantify cell-surface interactions.

Two functional polymer surfaces, phase separatedtyrosine-derived polycarbonate blends (DTR-PC) andconformational-based poly(2-hydroxyethyl methacrylate)brushes [poly(HEMA)], were analyzed using combinatorialmethodologies. The DTR-PC films, consisting ofhomopolymer and discrete composition blends oftyrosine-derived polycarbonates, were shown to havecompositionally dependent gene expression profiles withthe blends differing significantly from the respectivehomopolymers. Figure 1 illustrates the effect that polymerblending has on cell spreading; the extension and distortionof the lamellapodia increase and the cells appear to spreadless in the blend samples with increasing DTO content.The surface properties from these discrete films will beused to establish correlations and limitations for comparingmeasurements from discrete samples and single andmulti-variable continuous gradient substrates.

Figure 1: AFM micrographs of the tyrosine-derived polycarbonatehomopolymers and discrete blends show compositionally dependentphase separation, which is reflected in the immuno-fluorescentstaining for actin (red, cell spreading) and vinculin (green, focaladhesion contacts) on MC3T3-E1 osteoblasts.

Figure 2: Schematic representation of the poly(HEMA)-FNgradient and Fibroblast cell distribution.

Poly(HEMA) gradients were prepared to studymolecular interactions and cell conformation onfibronectin (FN) coated poly(HEMA) by combining“controlled” free radical polymerization with gradientpreparation technology. This gradient covers“mushroom” to “brush” regimes in order to determinehow grafting density influences protein adsorption andcellular response as shown in Figure 2. The numberof cells, their shape, and size were thus correlated tothe density of fibronectin across the gradient.

In summary, the tools developed in this programwill enable the design of material libraries to be usedto probe the behaviors of cells.


N.D. Gallant, L.O. Bailey, C. Simon, Jr., T.W. Kee,Y. Mei, J.S. Stephens, E.J. Amis (Polymers Division,NIST); K. Langenbach, J.T. Elliot (BiotechnologyDivision, NIST); J. Kohn, A. Rege, J. Schutt (RutgersUniversity & The New Jersey Center for Biomaterials)

Biomaterials

33

Biomaterials

Cell Response to Tissue Scaffold Morphology

Industrial and regulatory sectors have expresseda need for standards and new metrologies relatingto properties of tissue scaffolds for regenerativemedicine. We seek to meet these needs in severalareas where the criteria are clear, and to helpclarify industrial and regulatory needs in otherareas where such clarification is required. We aredeveloping a reference scaffold for porosity andpermeability. Also, we are developing metrologiesfor establishing the relationship between scaffoldporosity/morphology and cell response, forassessing the ability of a tissue scaffold to safelyhost cytokine, and for quantifying mechanicalstimulation requirements for cells — at the cellularlevel — from macroscopic inputs.

Marcus T. Cicerone

In the field of regenerative medicine, one seeks to guide cell differentiation and proliferation, and

production of the extracellular matrix through functionalproperties of 3D tissue scaffolds. Developing the abilityto guide such cell behaviors requires first the ability tocharacterize and assess properties of tissue scaffoldsas they relate to cell response. This, in turn, requireswell-defined physical and biological systems for whichquantitative rules can be formulated and verified.

We are developing methods for quantitativelycharacterizing tissue scaffolds and the cellularresponses they elicit. There are three classes ofscaffold properties that we focus on relative to theirimpact on cell behavior; these are: (i) morphological/topological properties, (ii) mechanical properties, and(iii) ability of biodegradable scaffold materials to actas biopreservants in connection with hosting growthfactors and other cytokines.

We led a worldwide collaboration under ASTM with17 other laboratories to establish a series of referencescaffolds for porosity and permeability. Our primarycharacterization method for these scaffolds is based ontomographic image analysis of scaffold morphology.

We are developing metrologies for assessing osteoblastresponse to pore size distributions in tissue scaffolds basedon extracellular matrix (ECM) production. We are alsoinvestigating morphology effects on osteoblast responseto surface chemistry. The image analysis methodsdeveloped in the reference scaffold activity serve tosupport these efforts. The ability to uniformly andreproducibly seed 3D scaffolds with adherent cells isanother critical factor for quantifying links betweenscaffold morphology and cell response, and we havedeveloped methods to accomplish this.

We are using computational modeling coupled withhigh-resolution imaging, atomic force microscopy(AFM), and optical trapping to develop metrology inthe area of cell response to environmental mechanicalstresses. It is clear that mechanical stimulation isrequired for some cell types to differentiate properly.Thus, it is important to be able to measure preciselywhat stress conditions are necessary for properphenotypic expression for selected cell types. We arecollaborating with the Materials Reliability Divisionof MSEL to establish methods to quantify the stressconditions at the cellular level based on macroscopicforces placed on the scaffold construct. Our approachis to translate ranges of macroscopic stresses to localstresses experienced by cells using a finite elementmodel. These local stresses will be correlated withcell response in terms of ECM production.

Biopreservation of cytokines in tissue scaffolds is acomplex but important area of regenerative medicine thathas been historically underserved. We are collaboratingwith six academic and one national lab to create a holisticapproach to stabilizing proteins in solid hosts such as tissuescaffolds. We are leading the grant-writing efforts in thiscollaboration and are focusing on clarifying the relationshipbetween fast glassy dynamics and biopreserving abilityof a material, which we have already observed in neutronscattering experiments. In keeping with this goal, we areestablishing accessible time-resolved optical metrologiesfor measuring these dynamics.


J. Dunkers, F. Wang, J. Cooper, T. DuttaRoy,J. Stephens, F. Phelan, M.Y.M. Chiang, L. Henderson(Polymers Division, NIST); Tim Quinn (MaterialsReliability Division, NIST)

Figure 1: A reconstruction of a candidate reference scaffold,generated from a tomographic image. Each colored objectrepresents a separate unit cell within the pore structure of the scaffold.

34

3-Dimensional In Situ Imaging for Tissue Engineering:Exploring Cell /Scaffold Interaction in Real Time

Real time investigations of cell/scaffoldinteractions provide valuable information aboutthe dynamic nature of cells and their spatialarrangements with respect to the three-dimensional(3D) architecture of tissue engineering scaffolds.In situ imaging capabilities will enable determinationof the structure/function relationship of tissueengineering scaffolds and definition of thenecessary properties to promote tissueregeneration. We demonstrate tools forin situ imaging of cells/scaffold interactions.

Jean S. Stephens and Joy P. Dunkers

The ability to image live cells and their correspondinginteractions with the surrounding environment

provides critical information about the ability to promotedesired cellular activity (proliferation, differentiation,etc.) for tissue regeneration. In order to developin situ optical imaging capabilities, we must be ableto nondestructively and noninvasively image theinteractions at the cell/scaffold interface whilemaintaining cell viability.

In our laboratory, collinear optical coherentmicroscopy/confocal fluorescence microscopy(OCM/CFM) has successfully been used to imagethe 3D interconnected porous structure of polymericscaffolds. This system combines high spatial resolution(~1 µm), high sensitivity (>100 dB), and exceptionaldepth-of-penetration associated with OCM with the

fluorescent capabilities of CFM. This, therefore, allowsus to not only investigate the 3D scaffold, but also theuse of conventional fluorescent staining techniques toevaluate cellular response.

In order to perform live cell imaging, a systemor bioreactor that can sustain cell viability outside ofan incubator and allow for imaging was constructed(Figure 1). The bioreactor is a perfusion flowbioreactor. This design forces the media to flowthrough the scaffold, therefore ensuring nutrientdelivery and oxygen perfusion, as well as wasteremoval, throughout the entire structure. Also, adynamic cell culture creates an environment that bettermimics physiological conditions. The temperatureof the bioreactor system is maintained by circulatingwater (37 °C) through a copper element.

Figure 1: Bioreactor in OCM/CFM, open and top view.

Figure 2: Time-lapse images of cell movement.

Initial in situ imaging studies indicate themaintenance of cell viability, and we have successfullyimaged cells for several hours. The series of imagesin Figure 2 illustrate cell movement over a 2 hour timeperiod. The ability to collect images in real time willgive a great insight and understanding of how cellsare responding to different materials, scaffoldarchitectures, and culture conditions. These datawill provide new metrics for the evaluation oftissue engineering scaffolds.


J.A. Cooper, C.R. Snyder (Polymers Division,NIST)

Biomaterials

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Broadband CARS Microscopy for Cellular/Tissue Imaging

In many of the biological sciences, as well asmany areas of polymer science, there is a needfor high-resolution, noninvasive, and chemicallysensitive imaging. We have developed a broadbandcoherent anti-Stokes Raman scattering (CARS)microscopy that provides an unprecedentedcombination of imaging speed and spectral coverage(i.e., chemical sensitivity). Our current efforts arefocused on eliminating nonresonant backgroundeffects, which can limit sensitivity of the technique.

Marcus T. Cicerone

We have developed a broadband CARS microscopymethod which allows us to obtain vibrational

spectra in the range (500 to 3000) cm–1 in less than1/50th the time required to obtain similar spectra byspontaneous Raman. This development was reportedat the first meeting of National Institute for BiomedicalImaging and Bioengineering (NIBIB) grantees, inBethesda, Maryland, the 11th Annual Time ResolvedVibrational Spectroscopy Conference, and the2005 Biophysical Meeting.

One key to the method we have developed is thegeneration of a broadband continuum. Optical pumpingof a tapered silica fiber was used to generate broadbandcontinuum in the first prototype of this instrument.Accumulative photo-damage limits the lifetime of thetapered fiber, and seriously limits the power level ofthe light that can be generated, significantly restrictingthe taper fiber as a reliable light source for CARSmicroscopy. With the assistance of an outside vendor,we have designed and procured a photonic crystalfiber (PCF) that is sealed at the ends, and which avoidsthe above issues. The PCF did not show any sign ofdegradation after a month, under long-term irradiationof 40 kW peak power femtosecond laser pulses. Thisadvance provided ≈10-fold increase in signal levels,so that, in principle, we can gather broadband spectrain 1/500th the time required for spontaneous Ramanspectroscopy. In practice, this rate exceeds thecapabilities of the CCD camera, which therefore setsthe limits on data acquisition; a faster camera wouldallow higher data collection rates.

A blend of chemically similar biodegradablepolymers, abbreviated as DTE and DTO (see Figure1a), have induced remarkable low immune responseupon fibroblast cell adhesion. These two polymersphase-separate upon annealing, and since they havesimilar indices of refraction, optical microscopy cannotbe used to image the phase-separated domains. On theother hand, broadband CARS microscopy has thesensitivity to distinguish the two polymers. Figure 1shows the three-dimensional imaging of a 50/50

DTE/DTO blend sample. In this sample, the spatialresolution is approximately 0.4 µm. We are currentlyexploring the hypothesis that the low cellular immuneresponse to the blends has its origins in spatialpatterning of the adhesion proteins. We are workingto correlate the protein adsorption with spatialpatterning of DTO and DTE rich domains.

In Figure 2, bright circular features are triglyceridelipid droplets in adipocytes, and the more subduedquasi-circular objects are the cells. We were unableto image the presence of protein in the cytosol due tononresonant background. Detection of these proteinsis crucial to identifying cell type, and we are currentlyfocusing our efforts on substantially reducing theeffects of nonresonant background.


T.W. Kee, H. Zhao, J. Taboas (Polymers Division,NIST); W-J. Li, R. Tuan (NIH/NIAMS)

Figure 2: Micrograph of adipocyte. This image was obtained withoutthe use of contrast agents such as fluorescent stains; the 2845 cm–1

C-H stretch vibrational band was the only image contrast.

Figure 1: (a) Chemical structures of DTE and DTO. CARSimages of a 50/50 DTE/DTO blend at depth: (b) 0 µm, (c) 3 µm,(d) 6 µm. The white areas in these images are DTO; the blackregions are DTE.

Biomaterials

36

Biomaterials

Molecular Design and Combinatorial Characterizationof Polymeric Dental Materials

Polymeric dental materials are finding increasingapplications in dentistry and allied biomedicalfields. As part of a joint research effort supportedby the National Institute of Dental and CraniofacialResearch and also in collaboration with theAmerican Dental Association Health FoundationPaffenbarger Research Center, NIST is providingthe dental industry with a fundamental knowledgebase that will aid in the prediction of clinicalperformance of dental materials.

Joseph M. Antonucci and Sheng Lin–Gibson

In contrast to current methods that rely onone-specimen-at-a-time measurements, metrologies

based on combinatorial and high-throughput (C&HT)approaches can accelerate fundamental and appliedresearch in dental materials. For dental polymersand their derivatives (sealants, adhesives, restorativecomposites), many critical properties depend on thechemical, structural, and compositional nature of theinitial monomer (resin) system. For multiphase dentalmaterials, e.g., composites, similar factors govern thequality of the interphase between the silanized filler phaseand the resin matrix. The objective of this research wasto determine the feasibility of adapting C&HT techniquesto measure material properties and screen variousexperimental resin chemistries for molecular design ofnovel dental polymers and composites. The technologiesdeveloped to enable this research include nanoindentationand the fabrication of single component or multi-variablediscrete and continuous gradient films.

instability for mechanical measurements test. SIEBIMMon PMMA, a linear polymer, yielded a modulus comparableto that obtained by the 3-point bend test. Buckling patternsfrom cross-linked BisGMA/TEGDMA films (Figure 1)resulted in moduli with increased variability, i.e., thebuckling patterns were not straight, parallel lines.Reasons for this behavior are under study.

Figure 2: Elastic moduli of photopolymerized BisGMA-TEGDMAof different compositions as a function of irradiation time(represented as distance).

Figure 1: Buckling patterns of BisGMA-TEGDMA in massratios of 30:70 (left) and 70:30 (right).

BisGMA-TEGDMA networks with 2D gradients,varying in monomer composition and conversion,were fabricated with a broad conversion range for allmonomer compositions. Conversions were measuredusing near-IR spectroscopy, and elastic modulus andhardness. As shown in Figure 2, the conversion andthe mechanical properties correlated well.

Additional techniques with the potential for C&HTapproaches are being evaluated for their ability to screenother properties of dental materials, including the interfacialsilane chemistry and cellular response. Studies on theinterfacial chemistry have shown that covalent bondingof nanoparticles with the polymerized matrix resultedin well-dispersed composites. To screen the biologicalresponse to dental materials, methods to measure cellviability, apoptosis, and gene expression levels as afunction of vinyl conversion have been developed.


E.A. Wilder, K.S. Wilson, N.J. Lin, C.M. Stafford,L. Henderson (Polymers Division, NIST);P.L. Votruba–Drzal (Materials and ConstructionResearch Division, NIST)

Among the different resin chemistries underinvestigation, 2D compositional gradients using BisGMA-TEGDA were selected as the benchmark for developingmetrologies and rapid screening techniques for optimizinghardness, shrinkage, and biocompatibility. The elasticmodulus was determined by two methods, nanoindentationand SIEBIMM — a strain-induced elastic buckling

37

Safety and Reliability

from the macro to the micro. The scope of activitiesincludes the development and innovative use ofstate-of-the-art measurement systems; leadership inthe development of standardized test procedures andtraceability protocols; development of an understandingof materials in novel conditions; and development andcertification of Standard Reference Materials® (SRMs).Many of the tests involve extreme conditions, such ashigh rates of loading, high temperatures, or unusualenvironments (e.g., deep underwater). These extremeconditions often produce physical and mechanicalproperties that differ significantly from handbook valuesfor their bulk properties under traditional conditions.These objectives will be realized through innovativematerials property measurement and modeling.

We take for granted that the physical infrastructurearound us will perform day in and day out withconsistent reliability. Yet, failures occur when thesestructures degrade to where they no longer sustain theirdesign loads, or when they experience loads outsidetheir original design considerations. In addition, wehave become increasingly aware of our vulnerability tointentional attacks. The Safety and Reliability Programwithin MSEL was created to develop measurementtechnology to clarify the behavior of materials underextreme and unexpected loadings, to assess integrityand remaining life, and to disseminate guidance andtools to assess and reduce future vulnerabilities.

Project selection is guided by identification andassessment of the particular vulnerabilities withinour materials-based infrastructure, and focusing onthose issues that would benefit strongly by improvedmeasurements, standards, and materials data. This year,we have worked with the Department of HomelandSecurity and the Office of Science and TechnologyPolicy in developing the National Critical InfrastructureR&D Plan, which will provide guidance across muchof the national infrastructure. Ultimately, our goal isto moderate the effects of acts of terrorism, naturaldisasters, or other emergencies, all through improveduse of materials.

Our vision is to be the key resource within theFederal Government for materials metrologydevelopment as realized through the followingobjectives:■ Develop advanced measurement methods needed by

industry to address reliability problems that arise withthe development of new materials;

■ Develop and deliver standard measurements and data;

■ Identify and address vulnerabilities and neededimprovements in U.S. infrastructure; and

■ Support other agency needs for materials expertise.

This program responds both to customer requests(primarily other government agencies) and to theDepartment of Commerce 2005 Strategic Goal of“providing the information and framework to enablethe economy to operate efficiently and equitably.”For example, engineering design can produce safeand reliable structures only when the property datafor the materials are available and accurate. Equallyimportant, manufacturers and their suppliers need toagree on how material properties should be measured.

The Safety and Reliability Program works towardsolutions to measurement problems on scales ranging

The MSEL Safety and Reliability Program isalso contributing to the development of test methodstandards through committee leadership roles instandards development organizations such as theASTM International and the International StandardsOrganization (ISO). In many cases, industry alsodepends on measurements that can be traced toNIST SRMs.

In addition to the activities above, MSEL providesassistance to various government agencies on homelandsecurity and infrastructural issues. Projects includeassessing the performance of structural steels as part ofthe NIST World Trade Center Investigation, collaboratingwith both the Department of Transportation and theDepartment of Energy on pipeline safety and bridgeintegrity issues, advising the Bureau of Reclamation onmetallurgical issues involving pipelines and dams, andadvising the Department of the Interior on the structuralintegrity of the U.S.S. Arizona Memorial.

Contact: Chad R. Snyder

Program Overview

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Polymer Reliability and Threat Mitigation

This project is developing metrologies andpredictive models to test and predict the long-termreliability of polymers used in ballistic resistantarmor and machine readable travel documents.Use of these methods and models will enable oneto monitor the performance of polymeric materialswhile in use, elucidate how environmental andmechanical factors influence performance, andprovide a basis for estimating durability andestablishing care procedures.

Chad R. Snyder, Gale A. Holmes, andWalter G. McDonough

Ballistic Resistant Armor

In response to an apparent failure of ballistic resistant armor during first responder use, NIST’s Office of Law

Enforcement Standards initiated a research programdesigned to strengthen the certification process of theseprotective devices. We are working to identify and developanalytical metrologies for quantifying the mechanicalproperties and degradation pathways of ballistic fibers thatcomprise this armor, with the ultimate goal being anestimate of vest durability and care procedures.

as quantified through the method of Cuniff andAuerbach.[1] Ongoing research is examining the effectsof fold radius as well as the effects of repeated folding.

Complementing our mechanical properties studies,our research into the degradation pathways of PBOand PBO-like materials has made significant headway.In addition to completion of our review article,[2]

we have synthesized the model compounds2-phenylbenzoxazole and bis-1,4-(2-benzoxazolyl)phenylene, and their hydroxy analogs, and we arecurrently analyzing, through matrix assisted laserdesorption/ionization (MALDI) mass spectrometry,the degradation products resulting from exposure toour newly acquired solar simulator.

Machine Readable Travel DocumentsAs indicated in an October 14, 2004 press release

from the U.S. Government Printing Office (GPO),NIST is testing the candidates for the new U.S.electronic passports for their ability to meet durability,security, and electronic requirements. This newtechnology will eventually be incorporated intoelectronic U.S. passports to enhance the securityof millions of Americans traveling around the world.At the request of the U.S. Department of State, weparticipated in the WG3 (Working Group 3 of ISO)meeting of the Document Durability Task Force forthe EPassport in Tsukuba, Japan. The purpose of thetask force meeting was to update the participants on thestatus of the Test Specification for Machine ReadableTravel Documents (MRTD). The main recommendationfrom the meeting was that any proposed test specificationby ISO would serve as the guideline to help nationswriting requests for proposals to develop their ownMRTDs. Also, the task force chairs have decided touse more complex testing sequences to better representreal-world applications; this was in line with therecommendations made by NIST.

References1. P.M. Cunnif and M.A. Averback, 23rd Army Science

Conference, Assistant Secretary of the Army (Acquisition,Logistics and Technology), Orlando, FL (Dec. 2002).

2. G.A. Holmes, K. Rice, and C.R. Snyder, Journal ofMaterials Science, in press.

Contributors and CollaboratorsJ. Dunkers, C.M. Guttman, K. Flynn, J. Kim,

F.A. Landis, D. Liu, W. Wallace (Polymers Division,NIST); D. Novotny, J. Guerrieri, G. Koepke, M. Francis,N. Canales, P. Wilson (Electromagnetics Division, EEEL);K. Rice (Office of Law Enforcement Standards, EEEL);T. Dang (Air Force Office of Scientific Research)

This year, we have made considerable progress onmultiple fronts towards these goals for poly(benzoxazole)(PBO) ballistic fibers. The modified single fiberfragmentation test, developed last year, was used toexamine the effect of fiber fatigue on ballistic resistance.Figure 1 shows the effect of folding on the morphologyand mechanical properties of a PBO fiber. Our analysissuggests that, for this case, folding resulted in anestimated >10 % reduction in overall ballistic performance,

Figure 1: Top and Left: Micrograph and yield strength dataobtained from modified single fiber test on an unfolded PBO fiber;Bottom and Right: Micrograph and figure for a folded PBO fiber.

Safety and Reliability

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Polymers Division FY05 Annual Report Publication List


Characterization and Measurement

Characterization

D.L. VanderHart, E. Perez, A. Bello, J. Vasquez,and R. Quijada, “Effect of Tacticity on the Structure ofPoly(1-octadecane),” Polymer 205, 1877–1885 (2004).

Gelation, Diffusion, and the Glass Transition

P.A. Netz, F.W. Starr, M.C. Barbosa, andH.E. Stanley, “Computer Simulation of DynamicalAnomalies in Stretched Water,” Brazilian Journal ofPhysics 34, 24–31 (2004).

K. VanWorkum and J.F. Douglas, “EquilibriumPolymerization in the Stockmayer Fluid as a Model ofSupermolecular Self-Organization,” Physical Review E71, 031502 (2004).

Mass Spectrometry

M.A. Arnould, W.E. Wallace, and R. Knochenmuss,“Understanding and Optimizing the MALDI ProcessUsing a Heated Sample Stage: a 2,5-DihydroxybenzoicAcid Study,” Proceedings of the 52nd ASMS Conferenceon Mass Spectrometry and Allied Topics, May 2004,Nashville, TN.

H.C.M. Byrd, S. Bencherif, B.J. Bauer, K.L. Beers,Y. Brun, S. Lin–Gibson, and N. Sari, “Examinationof the Covalent Cationization Method Using NarrowPolydisperse Polystyrene,” Macromolecules 38,1564–1572 (2005).

K.M. Flynn, S.J. Wetzel, C.M. Guttman,M.A. Arnould, and L.A. Lewis, “MALDI-TOF-MSCharacterization of Polycyanoacrylate Generatedunder Acidic Conditions Using ‘Super Glue’ orthe Cyanoacrylate Finger Print Fuming Method,”Proceedings of the 52nd ASMS Conference onMass Spectrometry and Related Topics, May 2004,Nashville, TN.

C.M. Guttman, S.J. Wetzel, K.M. Flynn,B.M. Fanconi, D.L. VanderHart, and W.E. Wallace,“Matrix-Assisted Laser Desorption/IonizationTime-of-Flight Mass Spectrometry InterlaboratoryComparison of Mixtures of Polystyrene withDifferent End Groups: Statistical Analysis of MassFractions and Mass Moments,” Analytical Chemistry77, 4539–4548 (2005).

C.M. Guttman, S.J. Wetzel, K.M. Flynn,B.M. Fanconi, W.E. Wallace, and D.L. VanderHart,“International Interlaboratory Comparison of Mixturesof Polystyrenes with Different End Groups Obtainedby Matrix Assisted Laser Desorption/IonizationTime-of-Flight Mass Spectrometry (MALDI-TOF-MS):Preliminary Results,” Proceedings of the 52nd ASMSConference on Mass Spectrometry and Allied Topics,May 2004, Nashville, TN.

A.J. Kearsley, W.E. Wallace, and C.M. Guttman,“A Numerical Method for Mass Spectral Data Analysis,”Applied Mathematics Letters 18, 1412–1417 (2005).

Z. Vakili, J.E. Girard, C.M. Guttman, M.A. Arnould,and H.C.M. Byrd, “Analysis of Covalently CationizedPolystyrenes Using Liquid Chromatography andMass Spectrometry,” Proceedings of the 52nd ASMSConference on Mass Spectrometry and Related Topics,May 2004, Nashville, TN.

W.E. Wallace and C.M. Guttman, “Recent Advancesin Quantitative Synthetic-Polymer Mass Spectrometryat NIST,” Proceedings of the 52nd ASMS Conferenceon Mass Spectrometry and Allied Topics, May 2004,Nashville, TN.

W.E. Wallace, “Synopsis of the 2004 ASMS FallWorkshop on Polymer Mass Spectrometry,” Journalof the American Society for Mass Spectrometry 16,291–293 (2005).

S.J. Wetzel, C.M. Guttman, K.M. Flynn, andJ.J. Filliben, “The Optimization of MALDI-TOF-MSfor Synthetic Polymer Characterization by FactorialDesign,” Proceedings of the 52nd ASMS Conferenceon Mass Spectrometry and Allied Topics, May 2004,Nashville, TN.

S.J. Wetzel, C.M. Guttman, and J.E. Girard,“The Influence of Matrix and Laser Energy on theMolecular Mass Distribution of Synthetic Polymersobtained by MALDI-TOF-MS,” International Journalof Mass Spectrometry 238, 215–225 (2004).

Polymers Composites and Nanocomposites

M.Y.M. Chiang, X.F. Wang, and C.R. Schultheisz,“Prediction and Three-Dimensional Monte-CarloSimulation for Tensile Properties of UnidirectionalHybrid Composites,” Composites Science andTechnology 65, 1719–1727 (2005).

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X. Wang, M.Y.M. Chiang, and C.R. Snyder,“Monte-Carlo Simulation for the Fracture Processand Energy Release Rate of Unidirectional CarbonFiber-Reinforced Polymers at Different Temperatures,”Composites Part A: Applied Science andManufacturing 35, 1277–1284 (2004).

S. Bourbigot, D.L. VanderHart, J.W. Gilman,S. Bellayer, H. Stretz, and D.R. Paul, “Solid StateNMR Characterization and Flammability ofStyrene-Acrylonitrile Copolymer MontmorilloniteNanocomposite,” Polymer 45, 7627–7638 (2004).

B.H. Cipriano, S.R. Raghavan, and P.M. McGuiggan,“Surface Tension and Contact Angle Measurements ofa Hexadecyl Imidazolium Surfactant Adsorbed on aClay Surface,” Colloid and Surface A: Physiochemicaland Engineering Aspects 262, 8–13 (2005).

Polymer Crystallization

L. Granasy, T. Pusztai, T. Borzsonyi, J.A. Warren,and J.F. Douglas, “A General Mechanism ofPolycrystalline Growth,” Nature Materials 3,645–650 (2004).

G. Matsuba, K. Shimizu, H. Wang, Z.G. Wang,and C.C. Han, “The Effect of Phase Separation onCrystal Nucleation Density and Lamella Growthin Near-Critical Polyolefin Blends,” Polymer 45,5137–5144 (2004).

Electronics MaterialsE.K. Lin, Materials Science and Engineering

Laboratory. FY 2004 Programs and Accomplishments:MSEL Materials for Micro- and Optoelectronics, NISTInteragency/Internal Report (NISTIR) NISTIR 7129(2004).

Nanoporous Low-k Dielectric Thin Filmsand Dimensional Metrology

B.J. Bauer, “Transformation of Phase SizeDistribution into Scattering Intensity,” Journal ofPolymer Science: Part B Polymer Physics 42,3070–3080 (2004).

B.J. Bauer, R.C. Hedden, H.J. Lee, C.L. Soles, andD.W. Liu, “Determination of Pore Size Distribution inNano-Porous Thin Films from Small Angle Scattering,”Materials Research Society Symposium Proceedings,April 2003, San Francisco, CA.

R.C. Hedden, B.J. Bauer, and H.J. Lee,“Characterization of Nanoporous Low-k ThinFilms by Contrast Match SANS,” Materials ResearchSociety Symposium Proceedings, April 2003,San Francisco, CA.

R.C. Hedden, C. Waldfried, H.-J. Lee, andO. Escorcia, “Comparison of Curing Processes forPorous Dielectrics — Measurement from SpecularX-ray Reflectivity,” Journal of the ElectrochemicalSociety 151, F178–F181 (2004).

H.J. Lee, B.D. Vogt, C.L. Soles, D.W. Liu,B.J. Bauer, W.L. Wu, and E.K. Lin, “X-ray andNeutron Porosimetry as Powerful Methodologies forDetermining Structural Characteristics of PorousLow-k Thin Films,” Proceedings of the InternationalInterconnect Technology Conference (IITC) 2004Conference, June 2004, San Francisco, CA.

C.L. Soles, H.J. Lee, R.C. Hedden, D.W. Liu,B.J. Bauer, and W.L. Wu, “X-ray Reflectivity as aPowerful Metrology to Characterize Pores in Low-kDielectric Films,” Polymers for Microelectronics andNanoelectronics, 874, 209–222 (2004).

C.L. Soles, H.J. Lee, E.K. Lin, and W.L. Wu,Pore Characterization in Low-k Dielectric Films UsingX-ray Reflectivity: X-ray Porosimetry, NIST SpecialPublication 960–13 (2004).

B.D. Vogt, R.A. Pai, H.J. Lee, R.C. Hedden,C.L. Soles, W.L. Wu, E.K. Lin, B.J. Bauer, andJ.J. Watkins, “Characterization of Ordered MesoporousSilica Films Using Small-Angle Neutron Scatteringand X-ray Porosimetry,” Chemistry of Materials 17,1398–1408 (2005).

B.D. Vogt, H.J. Lee, W.L. Wu, and Y. Liu, “SpecularX-ray Reflectivity and Small Angle Neutron Scatteringfor Structure Determination of Ordered MesoporousDielectric Films,” Journal of Physical Chemistry B 109,18445–18450 (2005).

T. Hu, R.L. Jones, W.L. Wu, E.K. Lin, Q. Lin,D. Keane, S. Weigand, and J. Quintana, “Small AngleX-ray Scattering Metrology for Sidewall Angle andCross Section of Nanometer Scale Line Gratings,”Journal of Applied Physics 96, 1983–1987 (2004).

Advanced Lithography Fundamentals

E.L. Jablonski, V.M. Prabhu, S. Sambasivan,E.K. Lin, D.A. Fischer, D.L. Goldfarb, M. Angelopoulos,and H. Ito, “Surface and Bulk Chemical Propertiesof 157 nm Chemically Amplified Polymer Blends,”Proceedings of the 13th International Conferenceon Photopolymers, October 2003, Tamiment, PA.

R.L. Jones, T. Hu, E.K. Lin, W.L. Wu, D.L. Goldfarb,M. Angelopoulos, B.C. Trinque, G.M. Schmidt,M.D. Stewart, and C.G. Willson, “Formation ofDeprotected ‘Fuzzy Blobs’ in Chemically AmplifiedResists,” Journal of Polymer Science Part B —Polymer Physics 42, 3063–3069 (2004).


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R.L. Jones, V.M. Prabhu, D.L. Goldfarb, E.K. Lin,C.L. Soles, J.L. Lenhart, W.L. Wu, and M. Angelopoulos,“Correlation of the Reaction Front with Roughness inChemically Amplified Photoresists,” Polymers forMicroelectronics and Nanoelectronics 874, 86–97(2004).

J. Lenhart, D. Fischer, S. Sambasivan, E. Lin,R. Jones, C. Soles, W.L. Wu, D. Goldfarb, andM. Angelopoulos, “X-Ray Absorption Spectroscopy toProbe Surface Composition and Surface Deprotectionin Photoresist Films,” Langmuir 21, 4007– 4015 (2005).

V.M. Prabhu, E.J. Amis, D.P. Bossev, andN.S. Rosov, “Counterion Associative Behavior withFlexible Polyelectrolytes,” Journal of Chemical Physics121, 4424–4429 (2004).

V.M. Prabhu, M.X. Wang, E.L. Jablonski, C.L. Soles,B.D. Vogt, R.L. Jones, E.K. Lin, W.L. Wu, D.L. Goldfarb,M. Angelopoulos, and H. Ito, “Dissolution Fundamentalsin Model 248 nm and 157 nm Photoresists,” Proceedingsof the 13th International Conference on Photopolymers,October 2003, Tamiment, PA.

V.M. Prabhu, M.X. Wang, E.L. Jablonski,B.D. Vogt, E.K. Lin, W.L. Wu, D.L. Goldfarb,M. Angelopoulos, and H. Ito, “Fundamentals ofDeveloper-Resist Interactions for Line-Edge Roughnessand Critical Dimensions Control in Model 248 nm and157 nm Photoresists,” Proceedings of the SPIE,February 2004, Santa Clara, CA.

V.M. Prabhu, “Counterion Structure and Dynamicsin Polyelectrolyte Solutions,” Current Opinion inColloid and Interface Science 10, 2–8 (2005).

V.M. Prabhu, B.D. Vogt, W.-L. Wu, E.K. Lin,J.F. Douglas, S.K. Satija, D.L. Goldfarb, and H. Ito,“In Situ Measurement of the Counterion Distributionwithin Ultrathin Photoresist Solid Films by Zero-Average Contrast Specular Neutron Reflectivity,”Langmuir 21, 6647–6651 (2005).

G.M. Schmid, M.D. Stewart, C.Y. Wang, B.D. Vogt,V.M. Prabhu, E.K. Lin, and C.G. Willson, “ResolutionLimitation in Chemically Amplified PhotoresistSystems,” Proceedings of SPIE — Advances in ResistTechnology and Processing, XXI, February 2004,Santa Clara, CA.

B.D. Vogt, E.K. Lin, W.L. Wu, and C.C. White,“Effect of Film Thickness on the Validity of theSauerbrey Equation for Hydrated PolyelectrolyteFilms,” Journal of Physical Chemistry B 108,12685–12690 (2004).

B.D. Vogt, C.L. Soles, C.Y. Wang, V.M. Prabhu,P.M. McGuiggan, J.F. Douglas, E.K. Lin, W.L. Wu,S.K. Satija, D.L. Goldfarb, and M. Angelopoulos,“Water Immersion of Model Photoresists: InterfacialInfluences on Water Concentration and SurfaceMorphology,” Microlithography, Microfabricationand Microsystems 4, 013003 (2005).

B.D. Vogt, C.L. Soles, V.M. Prabhu, S.K. Satija,E.K. Lin, and W.L. Wu, “Water Distribution withinImmersed Polymer Films,” Proceeding of the SPIEMicrolithography 2005, 9, San Jose, CA, 2005.

C.L. Soles, J.F. Douglas, and W.L. Wu,“Dynamics of Thin Polymer Films: Recent Insightsfrom Incoherent Neutron Scattering,” Journal ofPolymer Science Part B — Polymer Physics 42,3218–3234 (2004).

D.L. VanderHart, V.M. Prabhu, and E.K. Lin,“Proton NMR Determination of Miscibility in a BulkModel Photoresist System: Poly(4-hydroxystyrene) andthe Photoacid Generator, Di-(t-butylphenyl) IodoniumPerfluorooctanesulfonate,” Chemistry of Materials 16,3074–3084 (2004).

Organic Electronics/Dielectric Measurements

J. Obrzut and A. Anopchenko, “Input Impedanceof a Coaxial Line Terminated with a Complex GapCapacitance — Numerical and Experimental Analysis,”IEEE Transactions on Instrumentation andMeasurement 53, 1197–1201 (2004).

J. Obrzut and K. Kano, “Impedance and NonlinearDielectric Testing at High AC Voltages UsingWaveforms,” IEEE Transactions on Intrumentationand Measurement 54, 1570–1574 (2005).

B.D. Vogt, H.-J. Lee, V.M. Prabhu,D.M. DeLongchamp, S.K. Satija, E.K. Lin,and W.L. Wu, “X-Ray and Neutron ReflectivityMeasurements of Moisture Transport Through ModelMultilayered Barrier Films for Flexible Displays,”Journal of Applied Physics 97, 114509 (2005).

B.D. Vogt, V.M. Prabhu, C.L. Soles, S.K. Satija,E.K. Lin, and W.L. Wu, “Control of Moisture at BuriedPolymer/Alumina Interfaces through Substrate SurfaceModification,” Langmuir 21, 2460–2464 (2005).

B.D. Vogt, C.L. Soles, H.J. Lee, E.K. Lin, andW.L. Wu, “Moisture Absorption into UltrathinHydrophilic Polymer Films on Different SubstrateSurfaces,” Polymer 46, 1635–1642 (2005).


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Biomaterials

Combinatorial Libraries for Rapid Screening

E.J. Amis, S.B. Kennedy, A.M. Forster, andN.R. Washburn, “Spatial Correlations and RobustStatistical Analysis for Combinatorial Methodologies,”Proceedings of the 7th World Biomaterials Congress,478, May 2004, Sidney, Australia.

E.J. Amis, N.R. Washburn, C.G. Simon, Jr., andS.B. Kennedy, “Gradient Libraries for Combinatorialand High-Throughput Investigations of PolymericBiomaterials,” Proceedings of the 7th World BiomaterialsCongress, 1265, May 2004, Sidney, Australia.

N. Eidelman and C.G. Simon, Jr., “Characterizationof Combinatorial Polymer Blend CompositionGradients by FTIR Microspectroscopy,” Journal ofResearch of the National Institute of Standards andTechnology 109, 219–231 (2004).

N.J. Lin, L.O. Bailey, and N.R. Washburn,“Combinatorial Methods to Assess Cellular Responseto Bis-GMA/TEGDMA Vinyl Conversion Levels,”Society for Biomaterials 30th Annual Meeting andExposition.

Y. Mei, T. Wu, C. Xu, K.J. Langenbach, J.T. Elliott,B.D. Vogt, K.L. Beers, E.J. Amis and N.R. Washburn,“Combinatorial Studies of the Effect of PolymerGrafting Density on Protein Absorption and CellAdhesion,” ACS Polymer Preprints, Washington, DC,2005.

N.R. Washburn, M.D. Weir, W.J. Li, and R.S. Tuan,“Combinatorial Screening of Chondrocyte Response toTissue Engineering Hydrogels,” Proceedings of the7th World Biomaterials Congress, 1269, May 2004,Sidney, Australia.

Bioanalysis of Polymeric Materials

M.L. Becker, L.O. Bailey, N.R. Washburn, J. Kohn,and E.J. Amis, “Gene Expression Profiles of Cellsin Response to Tyrosine Polycarbonate Blends,”The 7th New Jersey Symposium on BiomaterialsScience, October 2004, New Brunswick, NJ.

M.L. Becker, L.O. Bailey, and K.L. Wooley,“Peptide-Derivatized Shell-Cross-linked Nanoparticles.2. Biocompatibility Evaluation,” BioconjugateChemistry 15, 710–717 (2004).

M.L. Becker, L.O. Bailey, J.S. Stephens, A. Rege,J. Kohn, and E.J. Amis, “Cellular Response toPhase-Separated Blends of Tyrosine-DerivedPolycarbonates,” Polymer Material Science andEngineering (PMSE) Preprint, Washington, DC, 2005.

M.T. Cicerone, J.P. Dunkers, N.R. Washburn,F.A. Landis, and J.A. Cooper, “Optical CoherenceMicroscopy for In-situ Monitoring of Cell Growthin Scaffold Constructs,” Proceedings of the 7th WorldBiomaterials Congress, 584, May 2004, Sidney,Australia.

M.T. Cicerone, W.J. Li, R. Tuan, C.L. Soles, andB.M. Vogel, “Sustained Delivery of Stabilized Proteinsfrom Electrospun Tissue Scaffolds,” Proceedings ofthe 7th World Biomaterials Congress, 514, May 2004,Sidney, Australia.

T. Dutta Roy, J.J. Stone, E.H. Cho, S.J. Lockett, andF.W. Wang, “Mechanisms of Osteoblast Adhesion on3D Polymer Scaffolds Made by Rapid Prototyping,”Society for Biomaterials 30th Annual MeetingTransactions, 347, April 2005, Memphis, TN.

T. Dutta Roy, J.J. Stone, W. Sun, E.H. Cho,S.J. Lockett, F.W. Wang, and L. Henderson, “OsteoblastAdhesion on Tissue Engineering Scaffolds Made byBio-Manufacturing Techniques,” Proceedings of 2005American Society of Mechanical Engineers (ASME)International Mechanical Engineering Congress andExposition (IMECE), November 2005, Orlando, FL.

E. Jabbari, K.W. Lee, A.C. Ellison, M.J. Moore,J.A. Tesk, and M.J. Yaszemski, “Fabrication of ShapeSpecific Biodegradable Porous Polymeric Scaffoldswith Controlled Interconnectivity by Solid Free-FormMicroprinting,” Transactions of the 7th WorldBiomaterials Congress, 1348, May 2004, Sidney,Australia.

T.W. Kee and M.T. Cicerone, “A Simple Approachto One-Laser, Broadband Coherent Anti-Stokes RamanScattering Microscopy,” Optics Letters 29, 2701–2703(2004).

C.A. Khatri, G. Du, E.S. Wu, and F.W. Wang,“Focal Adhesions of Osteoblasts on Poly(D,L-lactide)/Poly(vinyl alcohol) Blends by Confocal FluorescenceMicroscopy,” Proceedings of the 7th WorldBiomaterials Congress, 609, May 2004, Sidney,Australia.

Y. Mei, T. Wu, C. Xu, K. Langenbach, J.T. Elliott,K.L. Beers, E.J. Amis, N.R. Washburn, andL. Henderson, “Control of Protein Absorption andCell Adhesion: Effect of Polymer Grafting Density,”ACS Polymer Preprints, Washington, DC, 2005.

S.N. Park, E.S. Wu, C.A. Khatri, H. Suh, andF.W. Wang, “Microstructures of Collagen-HyaluronicAcid Hydrogels by Two-Photon FluorescenceMicroscopy,” Proceedings of the 7th WorldBiomaterials Congress, 1496, May 2004, Sidney,Australia.


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C.G. Simon, Jr., “Imaging Cells on PolymerSpherulites,” Journal of Microscopy 216, 153–155(2004).

J.A. Tesk, “ASTM Task Force Open forDevelopment of Reference Scaffolds for TissueEngineered Medical Products (TEMPs),”Biomaterials FORUM 26, 14 (2004).

N.R. Washburn, M.D. Weir, F.W. Wang, andL.O. Bailey, “Measurement and Modulation ofCytokine Profiles Induced by Biomaterials,”Proceedings of the 7th World Biomaterials Congress,1339, May 2004, Sidney, Australia.

H.H.K. Xu and C.G. Simon, Jr., “Fast SettingCalcium Phosphate-Chitosan Scaffold: MechanicalProperties and Biocompatibility,” Biomaterials 26,1337–1348 (2005).

H.H.K. Xu, C.G. Simon, Jr., S. Takagi, L.C. Chow,and F.C. Eichmiller, “Strong, Macroporous and In-SituHardening Hydroxyapatite Scaffold for Bone TissueEngineering,” Biomaterials Forum 27, 14–19 (2005).

S. Yoneda, W.F. Guthrie, D.S. Bright, C.A. Khatri,and F.W. Wang, “In Vitro Biocompatibility ofHydrolytically Degraded Poly(D,L-lactic acid),”Proceedings of the 7th World Biomaterials Congress,1324, May 2004, Sidney, Australia.

K. Zhang, N.R. Washburn, J.M. Antonucci, andC.G. Simon, Jr., “In Vitro Culture of Osteoblasts withThree Dimensionally Ordered Macroporous Sol-gelBioactive Glass (3DOM-BG) Particles,” InternationalSymposium on Ceramics in Medicine (Bioceramics 17),December 2004, New Orleans.

K. Zhang, N.R. Washburn, and C.G. Simon, Jr.,“Cytotoxicity of Three-Dimensionally OrderedMacroporous Sol–Gel Bioactive Glass (3DOM-BG),”Biomaterials 26, 4532– 4539 (2005).

Molecular Advances in Dental Materials

L.E. Carey, H.H.K. Xu, C.G. Simon, Jr., S. Takagi,and L.C. Chow, “Premixed Rapid-Setting CalciumPhosphate Composites for Bone Repair,” Biomaterials26, 5002–5014 (2005).

M. Farahani, J.M. Antonucci, and C.M. Guttman,“Analysis of the Interactions of a Trialkoxysilane withDental Monomers by MALDI-TOF Mass Spectrometry,”ACS Polymer Preprints, August 2004, Philadelphia, PA.

S. Lin–Gibson, “The Use of MALDI-TOF MS and1H NMR as Complimentary Methods for ConfirmingComposition and Purity of Hydrogel Prepolymers,”Biomaterials FORUM 26, 10–11 (2004).

S. Lin–Gibson, M.L. Becker, K.S. Wilson, andN.R. Washburn, “Synthesis and Characterization ofBioactive PEGDM Hydrogels,” ACS PolymerPreprints, August 2004, Philadelphia, PA.

S. Lin–Gibson, E.A. Wilder, F.A. Landis,and P.L. Drzal, “Combinatorial Methods for theCharacterization of Dental Materials,” ACS PMSEPreprint, Washington, DC.

C.G. Simon, Jr., J.M. Antonucci, D.W. Liu, andD. Skrtic, “In Vitro Cytotoxicity of AmorphousCalcium Phosphate Composites,” Biomaterials 20,279–295 (2005).

E.A. Wilder, J.B. Quinn, and J.M. Antonucci,“Organogelators and their Application in DentalMaterials,” ACS Polymer Preprints, August 2004,Philadelphia, PA.

E.A. Wilder, K.S. Wilson, J.B. Quinn, D. Skrtic,and J.M. Antonucci, “Effect of an Organogelator onthe Properties of Dental Composites,” Chemistry ofMaterials 17, 2946–2952 (2005).

K.S. Wilson and J.M. Antonucci, “Structure–Property Relationships of Thermoset MethacrylateComposites for Dental Materials: Study of theInterfacial Phase of Silica Nanoparticle-FilledComposites,” ACS Polymer Preprints, August 2004,Philadelphia, PA.

K.S. Wilson, K. Zhang, and J.M. Antonucci,“Systematic Variation of Interfacial Phase Reactivity inDental Nanocomposites,” Biomaterials 26, 5095–5103(2005).

K. Zhang, N.R. Washburn, C.G. Simon, Jr.,J.M. Antonucci, and S. Lin–Gibson, “In Situ Formationof Blends by Photopolymerization of Poly(EthyleneGlycol) Dimethacrylate (PEGDMA) and Polylactide(PLA),” Biomacromolecules 6, 1615–1622 (2005).

Multiphase Materials

Nanothin Film Stability and Wetting

H. Grull, L.P. Sung, A. Karim, J.F. Douglas,S.K. Satija, M. Hayashi, H. Jinnai, T. Hashimoto, andC.C. Han, “Finite Size Effects on Surface Segregationin Polymer Blend Films Above and Below the CriticalPoint of Phase Separation,” Europhysics Letters 65,671–677 (2004).

K.M. Ashley, D. Raghavan, J.F. Douglas, andA. Karim, “Mapping Wetting/Dewetting TransitionLine in Ultrathin Polystyrene Films Combinatorially,”ACS PMSE Preprints, Washington, D.C.


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R. Song, M.Y.M. Chiang, A.J. Crosby, A. Karim,E.J. Amis, and N. Eidelman, “Combinatorial Peel Testsfor the Characterization of Adhesion Behavior ofPolymeric Films,” Polymer 46, 1643–1652 (2005).

M.Y.M. Chiang, R. Song, A.J. Crosby, A. Karim,C.K. Chiang, and E.J. Amis, “Combinatorial Approachto the Edge Delamination Test for Thin Film Reliability— Adaptability and Variability,” Thin Solid Films 476,379–385 (2005).

Processing Characterization

Nanomanufacturing

S.D. Hudson, F.R. Phelan, Jr., M.D. Handler,J.T. Cabral, K.B. Migler, and E.J. Amis, “MicrofluidicAnalogue of the 4-Roll Mill,” Applied Physics Letters85, 335–337 (2004).

S.D. Hudson, J.T. Cabral, W. Zhang, J.A. Pathak,and K.L. Beers, “Microfluidic Interfacial Tensiometry,”ACS PMSE Preprints, Washington, DC.

F.R. Phelan, Jr., S.D. Hudson, and M.D. Handler,“Fluid Dynamics Analysis of Channnel FlowGeometries for Materials Characterization inMicrofluidic Devices,” Rheologica Acta 45, 59–71(2005).

J.A. Pathak, D.J. Ross, and K.B. Migler, “ElasticFlow Instability, Curved Streamlines and Mixing inMicrofluidic Flows,” Physics of Fluids 16, 4028–4034(2004).

V. Percec, A.E. Dulcey, V.S.K. Balagurusamy,Y. Miura, J. Smidrkal, M. Peterca, S. Nummelin,U. Edlund, S.D. Hudson, P.A. Heiney, D.A. Hu,S.N. Magonov, and S.A. Vinogradov, “Self-Assemblyof Amphiphilic Dendritic Dipeptides into HelicalPores,” Nature 430, 764–768 (2004).

K. Van Workum, K. Yoshimoto, J.J. de Pablo, andJ.F. Douglas, “Isothermal Stress and Elasticity Tensorsfor Ions and Point Dipoles Using Ewald Summations,”Physical Review E 71, 061102 (2005).

Polymer and Nanoclay Processing

A.J. Bur, Y.H. Lee, S.C. Roth, and P.R. Start,“Polymer/Clay Nanocomposites Compounding:Establishing an Extent of Exfoliation Scale UsingReal-Time Dielectric, Optical and FluorescenceMonitoring,” ACS Polymer Preprints, August 2004,Philadelphia, PA.

A.J. Bur, S.C. Roth, M.A. Spalding, D.W. Baugh,K.A. Koppi, and W.C. Buzanowski, “TemperatureGradients in the Channels of a Single-Screw Extruder,”Polymer Engineering and Science 44, 2148–2157(2004).

R.D. Davis, A.J. Bur, M. McBrearty, Y.-H. Lee,J.W. Gilman, and P.R. Start, “Dielectric SpectroscopyDuring Extrusion Processing of Polymer Nanocomposites:A High Throughput Processing/CharacterizationMethod to Measure Layered Silicate Content andExfoliation,” Polymer 45, 6487–6493 (2004).

Y.-H. Lee, A.J. Bur, S.C. Roth, and P.R. Start,“Impact of Exfoliated Silicate on the DielectricRelaxation of Nylon 11 Nanocomposites in the Meltand Solid States,” ACS PMSE Preprints, August 2004,Philadelphia, PA.

Y.-H. Lee, A.J. Bur, S.C. Roth, and P.R. Start,“Accelerated Alpha Relaxation Dynamics in theExfoliated Nylon 11/Clay Nanocomposite Observedin the Melt and Semi-Crystalline State By DielectricSpectroscopy,” Macromolecules 38, 3828–3837 (2005).

Y.-H. Lee, A.J. Bur, S.C. Roth, P.R. Start, andR.H. Harris, “Monitoring the Relaxation Behaviorof Nylon/Clay Nanocomposites in the Melt with anOnline Dielectric Sensor,” Polymers for AdvancedTechnologies 16, 249–256 (2005).

N. Noda, Y.-H. Lee, A.J. Bur, V.M. Prabhu,C.R. Snyder, S.C. Roth, and M. McBrearty,“Dielectric Properties of Nylon 6/Clay Nanocompositesfrom On-Line Process Monitoring and Off-LineMeasurements,” Polymer 46, 7201–7217 (2005).

W.J. Wang, S.B. Kharchenko, K.B. Migler, andS. Zhu, “Triple-Detector GPC Characterization andProcessing Behavior of Long-Chain-BranchedPolyethylene Prepared by Solution Polymerizationwith Constrained Geometry Catalyst,” Polymer 45,6495–6505 (2004).

Nanotubes

D. Fry, B. Langhorst, H. Kim, E.A. Grulke,H. Wang, and E.K. Hobbie, “Anisotropy Of ShearedCarbon Nanotube Suspensions, Physical Review Letters95, 038304 (2005).

E.K. Hobbie, “Optical Anisotropy of NanotubeSuspensions,” Journal of Chemical Physics 121,1029–1037 (2004).

S.B. Kharchenko, J.F. Douglas, J. Obrzut,E.A. Grulke, and K.B. Migler, “Flow-inducedProperties of Nanotube-Filled Polymer Materials,”Nature Materials 3, 564 –568 (2004).

P.M. McGuiggan, “Friction and AdhesionMeasurements between a Fluorocarbon Surface and aHydrocarbon Surface in Air,” Journal of Adhesion 80,395– 408 (2004).


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H. Wang, W. Zhou, D.L. Ho, K.L. Winey,J.E. Fischer, C.J. Glinka, and E.K. Hobbie, “DispersingSingle-Wall Carbon Nanotubes with Surfactants:A Small Angle Neutron Study,” Nanoletters 4,1789–1793 (2004).

T. Kashiwagi, F. Du, K.I. Winey, K.M. Groth,J.R. Shields, S.P. Bellayer, H. Kim, and J.F. Douglas,“Flammability Properties of Polymer Nanocompositeswith Single-walled Carbon Nanotubes: Effects ofNanotube Dispersion and Concentration,” Polymer 46,471– 481 (2005).

Multivariant Measurement Methods

Combinatorial Methods Development

W. Zhang, M.J. Fasolka, A. Karim, and E.J. Amis,“An Informatics Infrastructure for Combinatorial andHigh-Throughput Materials Research Built on OpenSource Code,” Measurement Science and Technology16, 261–269 (2005).

S. Ludwigs, K. Schmidt, C.M. Stafford,M.J. Fasolka, A. Karim, E.J. Amis, R. Magerle, andG. Krauch, “Combinatorial Mapping of the PhaseBehavior of ABC Triblock Terpolymers in Thin Films:Experiments,” Macromolecules 38, 1850–1858 (2005).

D. Julthongpiput, W. Zhang, and M.J. Fasolka,“Combinatorial and High-Throughput Microscopy forThin Film Research,” Proceedings Microscopy andMicroanalysis, 2004 (Savannah, GA).

Adhesion and Mechanical Properties

M.Y.M. Chiang, D. Kawaguchi, and C.M. Stafford,“Combinatorial Approaches for Characterizing ThinFilm Bond Strength,” The Symposium CombinatorialApproaches to Materials, the American ChemicalSociety (ACS), Washington, DC.

M.Y.M. Chiang, C.M. Stafford, R. Song, andA.J. Crosby, “High-Throughput Approach to Studythe Effects of Polymer Annealing Temperature and Timeon Adhesion,” Proceedings of 28th Annual Meeting ofAdhesion Society, 205–207, Mobile, AL.

A. Chiche, W. Zhang, C.M. Stafford, and A. Karim,“A New Design for High-Throughput Peel Tests:Statistical Analysis and Example,” MeasurementScience and Technology 16, 183–190 (2005).

A.J. Crosby, M.J. Fasolka, and K.L. Beers,“High-Throughput Craze Studies in Gradient ThinFilms Using Ductile Copper Grids,” Macromolecules37, 9968–9974 (2004).

A.M. Forster, W. Zhang, and C.M. Stafford,“A Multilens Measurement Platform forHigh-Throughput Adhesion Measurements,”Measurement Science and Technology 16, 81–89(2005).

A.M. Forster, W. Zhang, and C.M. Stafford,“The Development of a High-Throughput AxisymmetricAdhesion Test,” Proceedings of the 28th AnnualMeeting of Adhesion Society, 399–401, Mobile, AL.

S. Guo, M.Y. Chiang, and C.M. Stafford, “ElasticInstability of Multilayer Films Coated on Substrates,”Proceedings of the 28th Annual Meeting of AdhesionSociety, 67–69, Mobile, AL.

S. Guo, C.M. Stafford, and M.Y. Chiang, “StressAnalysis for Combinatorial Buckling-Based Metrologyof Thin Film Modulus,” Proceedings of the 28thAnnual Meeting of Adhesion Society, 236–237,Mobile, AL.

C. Harrison, C.M. Stafford, W. Zhang, andA. Karim, “Sinusoidal Phase Grating Created by aTunably Buckled Surface,” Applied Physics Letters 85,4016–4018 (2004).

S. Moon, A. Chiche, A.M. Forster, W. Zhang, andC.M. Stafford, “Evaluation of Temperature-DependentAdhesive Performance via Combinatorial Probe TackMeasurements,” Review of Scientific Instruments 76,062210 (2005).

C.M. Stafford, “A New ‘Wrinkle’ in Nanometrology,”Optical Engineering Magazine, November/December,48 (2004).

C.M. Stafford, S. Guo, M.Y.M. Chiang, andC. Harrison, “Combinatorial and High-ThroughputMeasurements of the Modulus of Thin Polymer Films,”Review of Scientific Instruments 76, 062207 (2005).

E.A. Wilder, S. Guo, M.Y. Chiang, and C.M. Stafford,“High Throughput Modulus Measurements of SoftPolymer Networks,” ACS Polymer Preprints, ACS FallMeeting 2005 (Washington, DC).

Polymer Formulations

K.L. Beers, T. Wu, and C. Xu, “ATRP inMicrochannels,” ACS Polymer Preprints, ACS FallMeeting 2005 (Washington, DC).

A.J. Bur, Z.T. Cygan, K.L. Beers, and S.E. Barnes,“Monitoring Polymerization in Microfluidic FlowChannels Using Spectroscopy Methods,” Proceedingsof the Annual Technical Meeting, Society of PlasticsEngineers, May 2005 (Boston, MA).


46

J.T. Cabral and J.F. Douglas, “Propagating Wavesof Network Formation Induced by Light,” Polymer 46,4230– 4241 (2005).

J.T. Cabral and A. Karim, “Discrete CombinatorialInvestigation of Polymer Mixture Phase Boundaries,”Measurement Science and Technology 16, 191–198(2005).

Z.T. Cygan, J.T. Cabral, K.L. Beers, and E.J. Amis,“Microfluidic Platform for Generation of Organic PhaseMicroreactors,” Langmuir 21, 3629–3634 (2005).

A.I. Norman, D.L. Ho, A. Karim, and E.J. Amis,“Phase Behavior of Diblock Copoly(ethylene oxide-butylene oxide), E18B9 in Water by Small AngleNeutron Scattering,” Journal of Colloid and InterfaceScience 288, 155–165 (2005).

J.A. Pathak, R.F. Berg, and K.L. Beers,“Development of a Microfluidic Rheometer forComplex Fluids,” ACS PMSE Preprints, ACS FallMeeting 2005 (Washington, DC).

H.J. Walls, R.F. Berg, and E.J. Amis, “Multi-sampleCouette Viscometer for Polymer Formulations,”Measurement Science and Technology 16, 137–143(2005).

T. Wu, Y. Mei, J.T. Cabral, C. Xu, and K.L. Beers,“A New Synthetic Method for Controlled PolymerizationUsing a Microfluidic System,” Journal of the AmericanChemical Society 126, 9880–9881 (2004).

T. Wu, Y. Mei, C. Xu, H.C.M. Byrd, and K.L. Beers,“Block Copolymer PEO-b-PHPMA Synthesis UsingControlled Radical Polymerization on a Chip,”Macromolecular Rapid Communications 26,1037–1042 (2005).

C. Xu, T. Wu, C.M. Drain, J.D. Batteas, andK.L. Beers, “Microchannel Confined Surface InitiatedPolymerization,” Macromolecules 38, 6–8 (2005).

C. Xu, T. Wu, C.M. Drain, J.D. Batteas, and K.L. Beers, “Synthesis of Gradient CopolymerBrushes via Surface Initiated Atom Transfer RadicalCopolymerization,” ACS Polymer Preprints, ACS FallMeeting 2004 (Philadelphia, PA).

Scanned Probe Micropscopy

L.S. Goldner, M.J. Fasolka, and S.N. Goldie,“Measurement of the Local Diattenuation andRetardance of Thin Polymer Films Using NearField Polarimetry,” Applications of Scanned ProbeMicroscopy to Polymers, edited by J.D. Batteas andG. Walker (American Chemical Society, 2005).

L.S. Goldner, S.N. Goldie, M.J. Fasolka, F. Renaldo,J. Hwang, and J.F. Douglas, “Near-Field PolarimetricCharacterization of Polymer Crystallites,” AppliedPhysics Letters 85, 1338–1340 (2004).

X.H. Gu, T. Nguyen, L.P. Sung, M.R. VanLandingham,M.J. Fasolka, J.W. Martin, Y.C. Jean, D. Nguyen,N.K. Chang, and T.Y. Wu, “Advanced Techniques forNanocharacterization of Polymeric Coating Surfaces,”JCT Research 1, 191–200 (2004).

D. Julthongpiput, M.J. Fasolka, and E.J. Amis,“Gradient Reference Specimens for Advanced ScannedProbe Microscopy,” Microscopy Today 12, 48–51(2004).

Nanomaterials

M.J. Fasolka, D. Julthongpiput, W. Zhang, A. Karim,and E.J. Amis, “Gradient Micropatterns for SurfaceNanometrology and Thin Nanomaterials Development,”ACS PMSE Preprints, ACS Fall Meeting 2005(Washington, DC).

D. Julthongpiput, M.J. Fasolka, W. Zhang,T. Nguyen, and E.J. Amis, “Gradient ChemicalMicropatterns: A Reference Substrate for SurfaceNanometrology,” Nano Letters 8, 1535–1540 (2005).

Y. Park, Y.W. Choi, S. Park, C. Cho, M.J. Fasolka,and D. Sohn, “Monolayer Formation of PBLG-PEOBlock Copolymers at the Air–Water Interface,” Journalof Colloid and Interface Science 283, 322–328 (2005).


47

Polymers Division

Polymers Division

ChiefEric J. AmisPhone: 301–975–6762E-mail: [email protected]

Deputy ChiefChad R. SnyderPhone: 301–975–4526E-mail: [email protected]

NIST FellowWen-li WuPhone: 301–975–6839E-mail: [email protected]

Group LeadersCharacterization and MeasurementChad R. Snyder

Electronics MaterialsEric K. LinPhone: 301–975–6743E-mail: [email protected]

BiomaterialsMarcus T. CiceronePhone: 301–975–8104E-mail: [email protected]

Multiphase MaterialsAlamgir KarimPhone: 301–975–6588E-mail: [email protected]

Processing CharacterizationKalman MiglerPhone: 301–975–4876E-mail: [email protected]

Multivariant Measurement MethodsMichael FasolkaPhone: 301–975–8526E-mail: [email protected]

48

Research Staff

Amis, Eric [email protected], x-ray and light scatteringPolyelectrolytesViscoelastic behavior of polymersDendrimers and dendritic polymersFunctional biomaterialsCombinatorial methodsHigh-throughput experimentation

Antonucci, Joseph [email protected] polymer chemistryDental composites, cements and adhesionInitiator systemsInterfacial coupling agentsRemineralizing polymer systemsNanocomposites

Audino, Susan [email protected] spectrometry

Bailey, LeeAnn [email protected] biologyApoptosisInflammatory responsesFlow cytometryPolymerase chain reaction

Barnes, Susan E. [email protected] spectroscopy of polymersMicrofluidics technologyFluorescence spectroscopyOn-line monitoring of polymer melts/extrusion

Bauer, Barry [email protected] synthesisPolymer chromatographyMALDI mass spectroscopyThermal characterizationNeutron, x-ray and light scatteringDendrimers, metallic ions nanoclusterPorous low-k thin film characterizationCarbon nanotubes

Becker, Matthew [email protected] synthesisBlock copolymersPeptide synthesisPhage displayCombinatorial methodsPolymerase chain reaction

Beers, Kathryn [email protected] and high-throughput methodsPolymer formulationsMicrofluidics technologyPolymer synthesisControlled/living polymerizations

Blair, William [email protected] analysis by size exclusion

chromatographyMass spectrometry of polymersHigh temperature viscometryRayleigh light scatteringExtrusion plastometry

Bowen, Rafael L.*[email protected] compositesNovel monomer synthesis

Bur, Anthony [email protected] properties of polymersFluorescence and optical monitoring

of polymer processingPiezoelectric, pyroelectric polymersViscoelastic properties of polymers

Cabral, Joao+

[email protected] rapid prototypingPolymer phase separationMillifluidic measurements

Carey, Clifton M.*[email protected] plaqueMicroanalytical analysis techniquesFluoride efficacy for dental healthDe- and re-mineralizationPhosphate chemistryIon-selective electrodesToothpaste abrasion & erosion

Cherng, Maria*[email protected] phosphate biomaterials

Chiang, Chwan [email protected] polymersResidual stressImpedance spectroscopy

Research Staff

49

Chiang, Martin [email protected] mechanics

(finite element analysis)Strength of materials, fracture mechanicsEngineering mechanics of polymer-based

materialsBi-material interfaceImage quantitation

Choi, Kwang-Woo+

[email protected] for lithographyCritical dimension small angle x-ray scattering

(CD-SAXS)Extreme ultraviolet (EUV) lithography

Chow, Laurence C.*[email protected] phosphate compounds and biomaterialsTooth demineralization and remineralizationDental and biomedical cementsSolution chemistryDental caries prevention

Cicerone, Marcus [email protected] stabilizationGlass transition theoryOptical coherence microscopyTissue engineering scaffoldsConfocal microscopySpectroscopic imaging

Cipriano, Bani H.+Polymer rheology

Cooper, James [email protected] engineeringPolymer scaffoldsCell biologyOptical microscopy

Cygan, Zuzanna [email protected] formulationsFluorescent probe studiesMillifluidics of polymer solutionsCombinatorial and high-throughput methods

DeLongchamp, Dean [email protected] electronicsPolymer thin filmsPolyelectrolytesNear-edge x-ray absorption fine structure

spectroscopy (NEXAFS)Film electrochemistry

Dickens, Sabine*[email protected] compositesDental adhesivesTransmission electron microscopyRemineralizing resin-based calcium phosphate

composites and cements

Di Marzio, Edmund [email protected] mechanics of polymersPhase transitionsGlassesPolymers at interfaces

Douglas, Jack [email protected] on polymer solutions, blends, and

filled polymersTransport properties of polymer solutions and

polymers at interfacesScaling and renormalization group calculationConductivity/viscosity of nanoparticle filled

systemsCrystallization of polymers

Dunkers, Joy [email protected] coherence microscopyImage analysisFiber optic spectroscopyInfrared microspectroscopy of polymersConfocal fluorescence microscopy

Duppins, Gretchen E.*[email protected] Coordinator

Dutta Roy, [email protected] scaffolds for tissue engineeringCellular response to biomaterials

Eichmiller, Frederick C.*[email protected] dentistryCompositesDentin adhesivesPolymerization shrinkage

Eidelman, Naomi B.*[email protected] microspectroscopyCharacterization of dental tissues and materialsComposition of combinatorial polymer blendsAppplication of temperature and UV gradients

to polymers

Research Staff

50

Epps, Thomas H., [email protected] and high-throughput methodsBlock copolymersSelf-assembled structuresSurface energy patterning and controlSurfaces and interfacesScanning probe microscopy

Fagan, Jeffrey [email protected] separationsColloidal solutionsElectrooptical effectsCarbon nanotubes

Fasolka, Michael [email protected] and high-throughput methodsNIST Combinatorial Methods Center (NCMC)Self-assembled structuresSurface energy patterning and controlSurfaces and interfacesScanning probe microscopy

Flaim, Glenn M.*[email protected] dental composites

Floyd, Cynthia J. E.*[email protected] compositesNuclear magnetic resonance (NMR)

Flynn, Kathleen [email protected] flow rate measurementsSize exclusion chromatographyMass spectrometry of polymers

Fowler, Bruce [email protected] and Raman spectroscopyStructure of calcium phosphates, bones,

and teethComposites

Frukhtbeyn, Stanislav*

[email protected] phosphate compounds and biomaterialsTopical dental fluorides

Fry, Dan [email protected] alignment and dispersionCarbon nanotubesRheology

Gallant, Nathan [email protected] adhesion to biomaterialsCombinatorial screening of bioactive gradients

George, Laurie A.*[email protected] Administrator

Giuseppetti, Anthony A.*[email protected] of dental alloysScanning electron microcopyDental materials testing

Guo, Shu+

[email protected] mechanicsMechanical properties of thin filmsCombinatorial and high-throughput methodsPolymer thin filmsSurfaces and interfaces

Guttman, Charles [email protected] properties of polymersSize exclusion chromatographyMass spectrometry of polymers

Han, Charles [email protected] behavior of polymer blendsPhase separation kinetics of polymer blendsPolymer characterization and diffusionShear mixing/demixing and morphology control

of polymer blendsStatic, time resolved, and quasi-elastic scattering

Henderson, Lori [email protected]–property relationships of biomaterialsStructure–function of tissuesMolecular engineering of DNA and proteinsCellular physiology and assaysMolecular biology screeningPolymer synthesis and characterization

Hobbie, Erik [email protected] scattering and optical microscopyDynamics of complex fluidsShear-induced structures in polymer blends

and solutionsCarbon nanotubes suspensions and melts

Hodkinson, Christine S.*[email protected], Administrative Services

Research Staff

51

Holmes, Gale [email protected] interface scienceChemical-structure-mechanical property

relationships for:Polymer chemistryMass spectroscopyNanocomposites

Ballistic resistance

Hudson, Steven [email protected] microscopyPolymeric surfactant and interfacial dynamicsSelf-assemblyNanoparticle characterization and assemblyBiomaterials

Jones, Ronald [email protected] and x-ray scatteringNanoimprint lithographyNeutron reflectivityPolymer surfaces and thin filmsPolymer phase transitions and computer

simulation

Julthongpiput, Duangrut+

[email protected] and high-throughput methodsPolymer adhesion and mechanical propertiesScanning probe microscopy

Jung, Youngsuk+

[email protected] electronicsPolymer thin films and interfaces

Kang, [email protected] transform infrared spectroscopy (FTIR)Raman spectroscopyPolymers for lithographyPolymer thin films

Kano, [email protected] relaxation of polymersNonlinear dielectric and conductive

spectroscopyOrganic electronics

Karim, [email protected] and high-throughput methodsPatterning of thin-polymer blend films on

inhomogenous surfacesNeutron & x-ray reflection and scatteringAFM and optical microscopyNanofilled polymer filmsNanostructured materialsMetrology for nanoscale manufacturing

Kee, Tak+

[email protected] spectroscopyCoherent anti-Stokes Raman scattering (CARS)

microscopyTissue engineering scaffoldsConfocal microscopy

Kharchenko, Semen+

[email protected] optical propertiesBirefringenceViscoelastic properties

Khoury, Freddy [email protected], structure and morphology of

polymersAnalytical electron microscopy of polymersWide-angle and small-angle x-ray diffractionStructure and mechanical property relationships

Kim, Jae Hyun+

[email protected]/matrix interfacePolymer adhesion and mechanical propertiesPolymer compositesOptical coherence microscopy

Kipper, Matthew+

[email protected], chemotactic response to

biomaterialsCraniofacial tissue engineeringCell migration

Landis, Forrest [email protected] and melting of miscible

polymer blendsIonomersOptical coherence microscopyTissue engineered scaffoldsStatic small angle laser light scattering

Research Staff

52

Lee, Hae-Jeong+

[email protected] reflectivitySmall-angle neutron scatteringNanoimprint lithographyStructural characterization of low dielectric

constant thin filmsPorosimetry of porous thin films

Lee, Yu-Hsin (Mandy)+

[email protected] relaxation spectroscopyNanocompositesAtomic force microscopyRubber-toughened phenolic resinsDynamic mechanical analysis of polymer blends

Lin, Eric [email protected] thin films and interfacesPolymer photoresists for lithographyOrganic electronicsNanoimprint lithographySmall angle x-ray and neutron scatteringStatistical mechanicsX-ray and neutron reflectivity

Lin, Nancy [email protected] screening of scaffoldsCellular response to materials

Lin–Gibson, [email protected] of gels and nanocompositesMass spectrometry of synthetic polymersPolymer synthesis and modificationStructure and dynamics of nanocomposite

polymeric materialsTissue engineering hydrogels

Liu, [email protected] synthesisThermal gravimetric analysisDifferential scanning calorimetryGel permeation chromatographyInfrared spectroscopyNuclear magnetic resonance

Markovic, Milenko*[email protected] phosphate chemistryBiomineralization (normal and pathological)Crystal growth and dissolution kineticsHeterogeneous equilibria

McDonough, Walter [email protected] and cure monitoring polymer

compositesFailure and fracture of polymersPolymer composite interfacesDental materials

McGuiggan, [email protected] force microscopyViscoelastic propertiesSurface force measurements

Mei, Ying+

[email protected] synthesisPeptide synthesisBiodegradable polymersBiomimetic polymers

Meillon, Mathurin+

[email protected] rheologyCharacterization of processing aids

Migler, [email protected] of shear and pressure on phase behaviorFluorescence and optical monitoring of

polymer processingLiquid crystalsShear-induced two phase structuresPolymer slippage

Norman, Alexander+

[email protected] FormulationsWater soluble polymersMicroemulsionsNeutron and x-ray scattering from polymers

Obrzut, [email protected] relaxation spectroscopyElectronic properties of polymers and

compositesElectronic packagingMicrowave and optical waveguidesPhotoelectron spectroscopy (x-ray and UV)Reliability, stress testing

Parry, Edward E.*[email protected] appliance and crown and bridges

fabricationMachine shop applications

Research Staff

53

Pathak, Jai [email protected] and linear viscoelasticityPolymer dynamics and complex fluidsMicrofluidics

Phelan, Jr., Frederick [email protected] processingMicrofluidicsViscoelastic flow modelingChaotic mixingFlow in porous mediaLattice Boltzmann methods

Prabhu, Vivek [email protected] neutron scatteringPolyelectrolytesPolymers for lithographyFluorescence correlation spectroscopyPolymer thin filmsX-ray and neutron reflectivity

Quinn, Janet*[email protected] materials and material propertiesComposites

Richards, Nicola*[email protected] restorative materialsPolymer matrix composites

Rao, Ashwin [email protected] adsorptionThin films gelsFluorescence microscopyInterfacial rheology

Ro, Hyun Wook+

[email protected] lithographyLow-k dielectric thin filmsX-ray reflectivity

Sambasivan, Sharadha+

[email protected] x-ray absorption fine structure

spectroscopy (NEXAFS)Polymers for lithographyPolymer relaxation and tribologySelf assembled monolayer orientationCatalyst surface and bulk characterization

Schumacher, Gary E.*[email protected] dentistryCompositesDentin adhesives

Simon, Carl G., [email protected] in human plateletsBone marrow cell lineage/traffickingCombinatorial methods

Skrtic, Drago*[email protected] amorphous calcium phosphate-based

dental materials

Smith, Jack [email protected] scienceComputational modelingBiomaterials characterization

Snyder, Chad [email protected] crystallizationWAXD and SAXS of polymeric materialsThermal expansion measurementsThermal analysisThermal managementDielectric measurements and behaviorBallistic resistance

Soles, Christopher [email protected] dynamicsInelastic neutron scatteringLow-k dielectric thin filmsX-ray and neutron reflectivityPolymer thin films and lithographyIon beam scatteringNanoimprint lithography

Stafford, Christopher [email protected] and high-throughput methodsPolymer thin filmsPolymer adhesionMechanical properties of thin filmsSurfaces and interfaces

Start, Paul [email protected] electron microscopySol-gel processesSurfactants and interfacial tension

Research Staff

54

Stephens, Jean [email protected] coherence microscopyCell/scaffold interactionsTissue engineeringElectrospinningFiber morphology

Stone, Phillip [email protected] devicesDynamics of carbon nanotubesRheology

Sun, [email protected] biomaterialsFiber-matrix interfacial shear strengthCPC composites

Taboas, Juan [email protected] engineeringCell and tissue mechanicsMechanoactive bioreactorsTissue engineering

Takagi, Shozo*[email protected] diffractionCalcium phosphate biomaterialsTopical fluoridationDe- and remineralization

Tesk, John [email protected]: biomaterials; physical and

mechanical propertiesReference biomaterialsReference data for biomaterialsBiomaterials: orthopaedics, cardiovascular,

dental, opthalmic, & tissue engineeredmedical devices

Standards for medical devices

Tung, Ming S.*[email protected] of calcium phosphate and peroxide

compoundsRemineralization studiesStandard reference materials

VanderHart, David [email protected] of orientation in polymer fibers

and filmsSolid-state NMR of polymersMeasurement of polymer morphology at the

2–50 nm scalePulsed field gradient NMR

Vogel, Brandon [email protected] synthesisCombinatorial methodsDrug deliveryOrganic electronicsPolymer thin filmsSelf-assembled monolayers

Vogel, Gerald L.*[email protected] plaque chemistryChemistry of calcium phosphatesMicroanalytical techniquesFluoride chemistry

Vogt, Bryan [email protected] thin film propertiesX-ray and neutron reflectivityPolymers for lithographyQuartz crystal microbalanceOrdered mesoporous materialsOrganic electronics

Wallace, William [email protected] spectrometryGeometric data analysis methods

Wang, Francis [email protected] and photochemistry of polymersFluorescence spectroscopyCure monitoring of polymerizationTissue engineering

Wang, Xianfeng+

[email protected] Carlo simulationsFinite element modelingPolymer compositesMechanical propertiesImage quantitation

Weir, Michael*[email protected] engineeringDegradable hydrogelsGrowth factor dynamics and cellular response in

biomaterials

Wetzel, Stephanie [email protected] spectrometry of polymersChemometricsSize exclusion chromatography

Research Staff

55

Wilder, Elizabeth [email protected] behavior of polymer gelsMechanical properties of polymer compositesStructure-property relationships

Wu, [email protected] and x-ray scattering and reflectivityElectron microscopyMechanical behavior of polymers and

compositesPolymer surfaces and interfacesPolymer networks

Wu, Tao+

[email protected] formulationsPolymer synthesisInterfacial tension measurementsCombinatorial and high-throughput methods

Xu, [email protected] and high-throughput methodsPolymer formulationsSurface polymerization

Xu, Hockin*[email protected] tissue engineeringScaffold and cell interactionsFiber and whisker composites

Zhang, Wenhua+

[email protected] and high-throughput informaticsDatabase structureLaboratory automationPolymer thin films and blends

Zhao, Hongxia (Jessica)+

[email protected] fluid dynamicsData acquisitionMultivariate analysisSignal processing

* Research Associate+ Guest Scientist

Research Staff

57

National Institute of Standards and Technology

Materials Science and Engineering Laboratory

58

Polymers Division (854.00)