research article experiment research on bonding effect of...

Research ArticleExperiment Research on Bonding Effect ofPoly(lactic-co-glycolic acid) Device by SurfaceTreatment Method

Xiaopeng Wang1 Kun Lian2 and Tianning Chen1

1School of Mechanical Engineering State Key Laboratory for Strength and Vibration of Mechanical StructuresXirsquoan Jiaotong University Xirsquoan 710049 China2School of Nano-Science and Nano-Engineering (Suzhou) Collaborative Innovation Center of Suzhou Nano Science and TechnologyXirsquoan Jiaotong University Xirsquoan 710049 China

Correspondence should be addressed to Xiaopeng Wang xpwangmailxjtueducn

Received 4 September 2014 Accepted 21 December 2014

Academic Editor Long Yu

Copyright copy 2015 Xiaopeng Wang et alThis is an open access article distributed under the Creative CommonsAttribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

According to the low temperature and high effective bonding problem of microdevices made of degradable polymer PLGAchemical plasma andUV irradiationmethod are used to study the experimental surface treatment of PLGAfilms andmicrodevicesbonding process The results show that all three methods can reduce the surface contact angle of PLGA films the contact angleincreases with time at room temperature and the PLGA films contact angle is almost unchanged under refrigeration The PLGAfilm bonding temperature is significantly reduced after UV irradiation and the bonding interfaces also generate diffusion crosslinking layer are dense and uniform

1 Introduction

Copolymer poly(lactic-co-glycolic acid) (PLGA) is formedby the polymerization of lactic acid and glycolic acid and ithasmany advantages for example excellent biocompatibilitybiodegradability lack of toxicity and good thermoplasticityPLGA has been approved to be used in pharmaceuticalproducts or medical devices by the United States Foodand Drug Administration (US FDA) and is widely usedin pharmaceutical medical engineering and the modernindustrial field [1ndash4] Compared to traditional oral and injec-tion drug delivery the multicavity implantable controlled-release drug delivery system (MIDDS) made of PLGA canrelieve the suffering of the patients and improve the treatmenteffect dramatically because of its targeted releasing ratecontrolling large amount drug delivering and long periodreleasing [5ndash7] Shown in Figure 1 the micro MIDDS madeof PLGA with only 200120583m minimum structure width iscombined by bonding PLGA microstructures and films andthe parts are both fabricated by MEMS technologies Thusthe bonding quality between the microstructure and the film

is the key factor to achieve MIDDS predefined functionsIf the macromolecular drugs are filled into MIDDS suchas polypeptides and enzymes because the losing activitytemperature of the drug is usually between 40 and 70∘C highadhesive bonding or joining techniques cannot be employedTherefore drug delivery systems for PLGA micro-bondingtechnology to connect low temperature needs to be studied

According to polymer bonding theory the bondingprocess is divided into two steps adsorption and diffusionPolymer interface needs to have good adsorption capacityin order to protect the well-bonded prerequisite Interfaceadsorption performance is directly related to its surface freeenergy the surface free energy increases in correlation withthe adsorption capacity of the interface Many scholars havestudied the polymethyl methacrylate (PMMA) bonding pro-cess after surface treatment of polymer there are also somestudies about PLGA material surface treatment processesFor example after surface treatment of the PMMA and theresin (COC) sample by UVozone irradiation Tsao and hiscolleagues obtained bonding results of the PMMA and COCsubstrate by thermocompression bonding process at lower

Hindawi Publishing CorporationInternational Journal of Polymer ScienceVolume 2015 Article ID 825287 7 pageshttpdxdoiorg1011552015825287

2 International Journal of Polymer Science

DrugStructure interface

Seal film

Film interface

Structure

Figure 1 Schematic design of biodegradable microstructure fordrug delivery system

temperatures [8] Khorasani and his colleagues performedsurface treatment of PLLA and PLGA samples in an oxygenatmosphere using radio frequency (RF) plasma technologyand it was found that the process can greatly improve thesurface energy of the polymer material [9] Inagaki and hiscolleagues did surface modification of PLA film surface byAr-plasma and they found the Ar-plasma treatment did notlead to hydrophilic modification of the PLA film surface[10] At 20 Pa oxygen atmosphere and 50W 1356MHzglow discharge conditions Shen made a PLGA materialplasma treatment that enhanced the success rate of PLGAgrafted with collagen and improved the PLGA compatibilityin vivo ultimately [11] Jacobs and his colleagues used themedium pressure plasma treatment of PLA to investigate itssurface modification and water contact angle measurementsshowed an increased hydrophilic character of the foil surfaceafter plasma treatment [12] De Geyter and his colleaguesemployed dielectric barrier discharge operating in differentatmospheres (air nitrogen helium and argon) and atmediumpressure to modify the surface properties of PLA the resultsshowed that the discharge gas can have a significant influenceon the chemical composition of the PLA surfaces [13] Otherresearchers did many works about PLGAPLA surface treat-ment or modification and they found the biocompatibilityand thermal stability improvement or mechanical propertieschanges [14ndash23]

In this research the highly efficient and low temperaturethermocompression bonding process is proposed by increas-ing the surface energy of PLGA Chemical plasma and UVirradiation methods are used to modify the surface characterof PLGA films which aims to improve the face energy andsurface hydrophilicity lower the bonding temperature andprocessing conditions and optimize the bonding strengthand interface morphology

2 Experimental Methods

Poly(lactide-co-glycolide) (PLGA) was purchased from Lac-tel International Absorbable Polymers (Pelham AL USA)with lactide glycolide = 50 50 inherent viscosity range055ndash075 dLg specific gravity 134 gml modulus 2 times105 psi minus4 times 105 psi and amorphous melting point andglass transition temperature 40ndash50∘C The granular PLGA

materials are embossed to 400 120583m films at 70∘C using a self-made hot embossing machine

The most convenient method to assess the treatmenteffects is to measure the contact angle Since the materialhas a small surface contact angle it also has a higher surfacefree energy and an improved surface hydrophilicity Thissurface contact angle is measured using deionized water asthe reference fluid

21 Chemical Treatment PLGA films are separated into 7groups with 5 films for each immersed in 2NaOH solutionfor surface hydrolysis for 0min 5min 10min 20min40min 60min and 80min respectively and then washedby deionizedwaterTheir surface contact angles aremeasuredusing a contact angle instrument after drying in fluid nitrogenat room temperature

22 Plasma Treatments The Plasma-Enhanced CVD systemproduced by Japan SANKEN is used in plasma treatmentat the power of 50W and vacuum degree of 20 Pa withthe oxygen as the reactive gas The processes are as followsPLGA films are placed beneath the electrode in the cavitythe vacuum degree is reduced to 10 Pa and then maintainedat 20 Pa after filling with oxygen The glow discharge plasmatreatment could be proceeding between two electrodes byenabling the 50W power 1356MHz alternating currentaccording to the predetermined time For another 10min thefilms are taken out for measurement

23 UV Irradiation Treatment 126 nm and 172 nm UV areused to handle PLGA films and the excimer UV lampis provided by China Jiangsu Youwei Optoelectronics CoLtd Irradiation light is 70W boot time lt1 s illuminatedobject temperature lt40∘C and AC power is 220V50Hz Inthe experiment PLGA films are placed below the excimerUV lamp first then after completing predetermined timeirradiation the films are removed for measurement

24 Measurement and Assessment Contact angle measure-ment Contact Angle Meter (Type OCA20) produced byGermany Dataphysics is used to measure the contact angleby sessile drop method and deionized water as the referencesolutionThe results are recorded by the equipment automat-ically

Bonding strength measurement the tension test is per-formed by America Electron-Tensile Tester (Type 1095) andthe tensile rate is 1mmmin

Interface morphology measurement the films areobserved by Japan Olympus microscope (Type SZX16)

3 Results and Discussion

31 Chemical Treatment Result Figure 2 shows the chemicaltreatment results of the PLGA film Where 119909-axis representstime of chemical treatment 119910-axis represents the value ofthe contact angle From the figure we can see that NaOHtreatment reduces the surface contact angle of the PLGAfilm

International Journal of Polymer Science 3

0 10 20 30 40 50 60 70 80 900

10

20

30

40

50

60

70

80

Chemical treatment time (min)

Con

tact

angl

e(∘ )

Figure 2 Contact angle curve of PLGA films after chemicaltreatment

0 5 10 15 20 25 30 350

10

20

30

40

50

60

70

80

Oxygen plasma treatment time (min)

Con

tact

angl

e(∘ )

Figure 3 Contact angle curve of PLGAfilms after plasma treatment

and PLGA film surface contact angle drops from 70∘ to 52∘after 60 minutes

32 Plasma Treatment Result Figure 3 shows the Plasmatreatment results of the PLGA film where the 119909-axis repre-sents time of plasma treatment and the 119910-axis represents thevalue of the contact angle From the figure we can observe thefollowing plasma treatment reduces the surface contact angleof the PLGA film PLGA film surface contact angle dropsfrom 70∘ to 35∘ after 5 minutes PLGA film surface contactangle drops from 70∘ to 25∘ after 10 minutes PLGA filmcontact angle decreases to 15∘ after 30minutesThe Figure 3 issimilar to [13] results and [13] employed the oxygen plasmatreated PLGA film

33 UV Irradiation Treatment Result Figure 4 shows twokinds of UV irradiation treatment results of the PLGAfilm Where the 119909-axis represents time of UV irradiation

0 50 100 150 200 250 3000

10

20

30

40

50

60

70

80

UV irradiation time (s)

Con

tact

angl

e(∘ )

172nm UV light126nm UV light

Figure 4 Contact angle curves of PLGA films after two kinds of UVirradiation treatment

treatment 119910-axis represents the value of the contact angle998771 symbol represents the result of 172nm excimer ultravioletlight irradiation 998787 symbol represents the result of 126nmexcimer UV ligh irradiation From the figure we can observethe following UV irradiation treatment reduces the surfacecontact angle of the PLGA film PLGA film surface contactangle drops from 70∘ to 10∘ after about 50 seconds PLGA filmcontact angle change curves after 126 nm and 172 nm excimerultraviolet radiation have similar rules

34 The Ageing Effect of Surface Treatment Result The long-chain molecules of the polymer surface are broken intoshort-chainmolecules after plasma andUV treatment whichproduce many hydrophilic groups increasing the surfacehydrophilicity surface energy and adhesiveness But thiseffect may fade away over time due to its instability whichis called the ageing effect of surface treatment In orderto investigate the ageing effect of PLGA surface treatmentthe specimens after plasma and UV irradiation treatmentare placed in room temperature (20ndash25∘C) and refrigeratortemperature (4ndash6∘C) respectively the storage humidity isabout 40 and the contact angle curves are obtained Thusthe ageing effect of different treatments is obtained and theinfluence of temperature on ageing is also a preliminaryunderstanding

Figure 5 shows contact angle ageing results of PLGAfilm after two kinds of surface treatment where the 119909-axisrepresents the keep time after two kinds of surface treatment119910-axis represents the value of the contact angle ◼ symbolrepresents the contact angle kept at room temperature afterplasma treatment ◻ symbol represents the contact anglekept at room temperature after UV irradiation 998787 symbolrepresents the contact angle kept at freezer temperature afterplasma treatment998810 symbol represents the contact angle keptat freezer temperature after UV irradiation From the figurewe can analyze the following conclusions


0 5 10 15 20 25 30 350

10

20

30

40

50

60

70

80

Time (days)

Kept in room temperature after plasma treatmentKept in room temperature after UV irradiationKept in freezer after plasma treatment Kept in freezer after UV irradiation

Con

tact

angl

e(∘ )

Figure 5 Contact angle ageing curve of PLGA films after treatment

At room temperature the two kinds of the surface-treatedPLGA film surface contact angle continuously increase withtime The reason for this result is that PLGA film surface hasa large number of polar groups after treatment which resultsin the film surface retaining high energy and becomes veryunstable state The substance of the energy is lower when thesystem is more stable so the PLGA film surface contact angleincreases It will reduce the energy to the lowest point inorder to maintain the stability of the system

At room temperature the contact angle of PLGA filmafter the UV irradiation treatment changes quickly thecontact angle increases to 2 times the original after 1 dayincreases to 3 times the original after 3 days and subsequentlyincreases to 5 times the original after 6 days But at the sameroom temperature the contact angle of PLGA film linearlyincreases only 1 time after 10 days It is mainly due to theultraviolet irradiation mechanism is that PLGA long chain isinterrupted by high energy photon and becomes short chainduring storage at room temperature short-chain dynamicsregroup which results in the PLGA film surface contact angleincrease However the contact angle of PLGA film afterplasma treatment change not only have a short chain butthe air particles are ionized oxygen nitrogen and the surfaceof particles and the like polar groups react polar surfacegroups turn inward resulting aging resistance After plasmatreatment the surface of the PLGA film not only has shortchain but also has polar groups that react by ionized oxygennitrogen and the particles of surface Material surface polargroups turn inward causing ageing effectTherefore these twoapproaches obtained different change rates of contact angleFrom the data the polar group turning inward is slower thanthe dynamic reorganization of themolecular chain it also canbe obtained fromFigure 5 relative to the total change that thecontact angle change is not large at room temperaturewithin 1dayThe contact angles changed little when kept in the freezer

35 40 45 50 55 60 65 70 750

1

2

3

4

5

6

7

8

Max

imum

stre

ss (M

Pa)

Base lineAfter treatmentBefore treatment

Bonding temperature (∘C)

Figure 6 Bonding strength and temperature comparison chart

which shows that the low temperature environment is a goodway to preserve the films to be bonded The degradationproperty of polymers may also vary due to the long-chainsbeing broken But short term surface treatment will notinfluence the overall degradation performance due to thebulk degradation character of PLGA

Compared to the literatures study there are also someresults similar to ours For example Prasertsung and hiscolleagues did the similar research with this paper andthey studied the water contact angle of oxygen plasma-treated PLGA films after ageing at different ageing timesand temperatures They found that the films aged at highstorage temperature (20∘C 50∘C) exhibited a faster recoveryof contact angle compared to that at low storage temperature(5∘C) [24]

35 Effects on Bonding Temperature The ultimate goal ofPLGA surface treatment is to improve bonding propertiesand promote how different PLGA-based structures con-nected together well at the low temperatureThe relationshipsbetween bonding temperatures and bonding strength arestudied to show the effects of UV irradiation treatment Theexperimental films are also irradiated under 126 nm UV of70W UV light for 45 s and then bonding at pressure 4Nand time 45 s in different temperaturesThe bonding strengthis tested according to the method of experiment The oneswithout treatment are used as the control

Figure 6 shows bonding strength and temperature com-parison chart of the PLGA film Where 119909-axis represents thebonding temperature 119910-axis represents the tensile breakingstrength of the bonding base line means the minimumstrength value required to achieve bonding X symbol rep-resents the tensile breaking strength after surface treatment998771 symbol represents the tensile breaking strength withoutsurface treatment From this figure we can obtain the follow-ing conclusions when reaching the same bonding strength


(a)

(b1) (b2)

(c1) (c2)

200120583m

Figure 7 Interface morphology photographs of bonding effect times20 ((a) microstructure interface before bonding (b1) tearing interface 1without treatment at 65∘C (b2) tearing tnterface 2 without treatment at 65∘C (c1) tearing interface 1 after treatment at 45∘C (c2) tearinginterface 2 after treatment at 45∘C)

the bonding temperature after treatment is 20∘C lower thanwithout treatment and the satisfying bonding strengthwhichsurpasses the base line is obtained at about 45∘C This showsthat the bonding temperature is truly lowered by surfacetreatment and modification

36 Changes of Interface Morphology After being removedoff the new structure by bonding the morphology of thebonding interface is a good indication of the bonding effectWhen the tear interface is relatively smooth this indicates

that it do not produce an effective bonding When the tearinterface is very rough with lots of ravines and glitches thenthe bond is effective Figure 7 is enlarged 20 times showing theeffects of PLGA microstructure interface morphology pho-tographs of bonding where (a) is microstructure interfacemorphology photograph before bonding (b1) is tearing inter-face 1 morphology photograph without treatment bondingat 65∘C (b2) is tearing interface 2 morphology photographwithout treatment bonding at 65∘C (c1) is tearing interface 1morphology photograph afterUV treatment bonding at 45∘C


(c2) is tearing interface 2 morphology photograph after UVtreatment bonding at 45∘C

From Figure 7 we can obtain the following results Priorto bonding PLGA has smooth interface after bondingthe tear PLGA presents many broken gullies and differentinterfaces in the thermo compression bonding process thebonding interface does occur the molecular adsorptiondiffusion and crosslinking The maximum stress of tearingbefore treatment at 65∘C and ones after UV treatment at45∘C are nearly the same (Figure 6) But the ravines andburrs of UV treatment (Figures 7(b1) and 7(b2)) are muchdenser and uniformly distributed compared to the ones with-out treatment (Figures 7(c1) and 7(c2)) This phenomenoncoincides with the surface long-chains being broken by UVirradiation In summation theUV irradiation for PLGAfilmswill not only lessen the bonding process requirements butalso optimize the bonding interface to create a dense anduniformly diffusive layer

4 Conclusions

Chemical plasma and UV irradiation treatments can reducethe surface contact angle of PLGA and the latter is betterAfter processing of the ion and the ultraviolet irradiationPLGA film surface contact angle increases with time atroom temperature but the change is little within one dayRefrigeration preserved PLGA film surface contact anglechanges a little If the material bonding operation cannotbe carried out immediately after surface treatment it shouldbe kept in a low temperature environment The PLGA filmsurface after UV irradiation can reach ideal hot bondingstrength at about 45∘C and UV irradiation treatment processsignificantly reduces the temperature of the bonding PLGAfilm after the UV irradiation treatment can not only reducethe microstructure of the thermo compression bonding pro-cess condition but also be able to optimize themorphology ofthe coupling interface In addition the process can generate auniform and dense layer as possible diffusion of cross-linkingcoupling layer between the bonding interfaces

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work is supported by Natural Science Foundation ofChina (no 50705074) Collaborative Innovation Center ofSuzhou Nano Science and Technology and FundamentalResearch Funds for the Central Universities

References

[1] D Garlotta ldquoA literature review of poly(lactic acid)rdquo Journal ofPolymers and the Environment vol 9 no 2 pp 63ndash84 2001

[2] E Vey C Roger L Meehan et al ldquoDegradation mechanismof poly(lactic-co-glycolic) acid block copolymer cast films in

phosphate buffer solutionrdquo Polymer Degradation and Stabilityvol 93 no 10 pp 1869ndash1876 2008

[3] C Gao H Ma X Liu et al ldquoEffects of thermal treatment onthe microstructure and thermal and mechanical properties ofpoly(lactic acid) fibersrdquo Polymer Engineering and Science vol53 no 5 pp 976ndash981 2013

[4] JMChan L ZhangK P Yuet et al ldquoPLGA-lecithin-PEGcore-shell nanoparticles for controlled drug deliveryrdquo Biomaterialsvol 30 no 8 pp 1627ndash1634 2009

[5] H K Makadia and S J Siegel ldquoPoly Lactic-co-Glycolic Acid(PLGA) as biodegradable controlled drug delivery carrierrdquoPolymers vol 3 no 3 pp 1377ndash1397 2011

[6] X P Wang T N Chen and Z X Yang ldquoModeling andsimulation of drug delivery from a new type of biodegradablepolymer micro-devicerdquo Sensors and Actuators A Physical vol133 no 2 pp 363ndash367 2007

[7] Y Gao T Chen and X Wang ldquoNumerical modeling of a noveldegradable drug delivery system with microholesrdquoMicrosystemTechnologies vol 17 no 3 pp 387ndash394 2011

[8] C W Tsao L Hromada J Liu P Kumar and D L DeVoeldquoLow temperature bonding of PMMA and COC microfluidicsubstrates using UVozone surface treatmentrdquo Lab on a Chipvol 7 no 4 pp 499ndash505 2007

[9] M T Khorasani H Mirzadeh and S Irani ldquoPlasma surfacemodification of poly (L-lactic acid) and poly (lactic-co-glycolicacid) films for improvement of nerve cells adhesionrdquo RadiationPhysics and Chemistry vol 77 no 3 pp 280ndash287 2008

[10] N Inagaki K Narushima Y Tsutsui and Y Ohyama ldquoSurfacemodification and degradation of poly(lactic acid) films by Ar-plasmardquo Journal of Adhesion Science and Technology vol 16 no8 pp 1041ndash1054 2002

[11] H Shen X Hu F Yang J Bei and S Wang ldquoCombiningoxygen plasma treatment with anchorage of cationized gelatinfor enhancing cell affinity of poly(lactide-co-glycolide)rdquoBioma-terials vol 28 no 29 pp 4219ndash4230 2007

[12] T Jacobs H Declercq N De Geyter et al ldquoPlasma surfacemodification of polylactic acid to promote interaction withfibroblastsrdquo Journal of Materials Science Materials in Medicinevol 24 no 2 pp 469ndash478 2013

[13] N De Geyter RMorent T Desmet et al ldquoPlasmamodificationof polylactic acid in a medium pressure DBDrdquo Surface andCoatings Technology vol 204 no 20 pp 3272ndash3279 2010

[14] Z Karahaliloglu B Ercan S Chung E Taylor E B Denkbasand T J Webster ldquoNanostructured anti-bacterial poly-lactic-co-glycolic acid films for skin tissue engineering applicationsrdquoJournal of Biomedical Materials Research Part A vol 102 no 12pp 4598ndash4608 2014

[15] E Kiss E Kutnyanszky and I Bertoti ldquoModification ofpoly(lacticglycolic acid) surface by chemical attachment ofpolyethylene glycolrdquo Langmuir vol 26 no 3 pp 1440ndash14442010

[16] Y-C Huang C-C Huang Y-Y Huang and K-S ChenldquoSurfacemodification and characterization of chitosan or PLGAmembrane with laminin by chemical and oxygen plasma treat-ment for neural regenerationrdquo Journal of Biomedical MaterialsResearch Part A vol 82 no 4 pp 842ndash851 2007

[17] S Yoshida KHagiwara THasebe andAHotta ldquoSurfacemod-ification of polymers by plasma treatments for the enhancementof biocompatibility and controlled drug releaserdquo Surface andCoatings Technology vol 233 pp 99ndash107 2013


[18] Y Wang P Li and L Kong ldquoChitosan-modified PLGAnanoparticles with versatile surface for improved drug deliveryrdquoAAPS PharmSciTech vol 14 no 2 pp 585ndash592 2013

[19] F Sarasini D Puglia E Fortunati J M Kenny and C San-tulli ldquoEffect of fiber surface treatments on thermo-mechanicalbehavior of poly(lactic acid)phormium tenax compositesrdquoJournal of Polymers and the Environment vol 21 no 3 pp 881ndash891 2013

[20] Z W Xie G Buschle-Diller P Deinnocentes and R C BirdldquoElectrospun poly(DL)-lactide nonwoven mats for biomedicalapplication surface area shrinkage and surface entrapmentrdquoJournal of Applied Polymer Science vol 122 no 2 pp 1219ndash12252011

[21] B Asaithambi G Ganesan and S Ananda Kumar ldquoBio-composites development and mechanical characterization ofbananasisal fibre reinforced poly lactic acid (PLA) hybridcompositesrdquo Fibers and Polymers vol 15 no 4 pp 847ndash8542014

[22] N Zhou B Yu J Sun L Yao and Y Qiu ldquoInfluence ofchemical treatments on the interfacial properties of ramiefiber reinforced poly(lactic acid) (pla) compositesrdquo Journal ofBiobased Materials and Bioenergy vol 6 no 5 pp 564ndash5682012

[23] D Kurniawan B S Kim H Y Lee and J Y Lim ldquoAtmosphericpressure glow discharge plasma polymerization for surfacetreatment on sized basalt fiberpolylactic acid compositesrdquoComposites Part B Engineering vol 43 no 3 pp 1010ndash10142012

[24] I Prasertsung R Mongkolnavin S Damrongsakkul and CS Wong ldquoSurface modification of dehydrothermal crosslinkedgelatin film using a 50Hz oxygen glow dischargerdquo Surface andCoatings Technology vol 205 supplement 1 pp S133ndashS138 2010

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


DrugStructure interface

Seal film

Film interface

Structure

Figure 1 Schematic design of biodegradable microstructure fordrug delivery system

temperatures [8] Khorasani and his colleagues performedsurface treatment of PLLA and PLGA samples in an oxygenatmosphere using radio frequency (RF) plasma technologyand it was found that the process can greatly improve thesurface energy of the polymer material [9] Inagaki and hiscolleagues did surface modification of PLA film surface byAr-plasma and they found the Ar-plasma treatment did notlead to hydrophilic modification of the PLA film surface[10] At 20 Pa oxygen atmosphere and 50W 1356MHzglow discharge conditions Shen made a PLGA materialplasma treatment that enhanced the success rate of PLGAgrafted with collagen and improved the PLGA compatibilityin vivo ultimately [11] Jacobs and his colleagues used themedium pressure plasma treatment of PLA to investigate itssurface modification and water contact angle measurementsshowed an increased hydrophilic character of the foil surfaceafter plasma treatment [12] De Geyter and his colleaguesemployed dielectric barrier discharge operating in differentatmospheres (air nitrogen helium and argon) and atmediumpressure to modify the surface properties of PLA the resultsshowed that the discharge gas can have a significant influenceon the chemical composition of the PLA surfaces [13] Otherresearchers did many works about PLGAPLA surface treat-ment or modification and they found the biocompatibilityand thermal stability improvement or mechanical propertieschanges [14ndash23]

In this research the highly efficient and low temperaturethermocompression bonding process is proposed by increas-ing the surface energy of PLGA Chemical plasma and UVirradiation methods are used to modify the surface characterof PLGA films which aims to improve the face energy andsurface hydrophilicity lower the bonding temperature andprocessing conditions and optimize the bonding strengthand interface morphology

2 Experimental Methods

Poly(lactide-co-glycolide) (PLGA) was purchased from Lac-tel International Absorbable Polymers (Pelham AL USA)with lactide glycolide = 50 50 inherent viscosity range055ndash075 dLg specific gravity 134 gml modulus 2 times105 psi minus4 times 105 psi and amorphous melting point andglass transition temperature 40ndash50∘C The granular PLGA

materials are embossed to 400 120583m films at 70∘C using a self-made hot embossing machine

The most convenient method to assess the treatmenteffects is to measure the contact angle Since the materialhas a small surface contact angle it also has a higher surfacefree energy and an improved surface hydrophilicity Thissurface contact angle is measured using deionized water asthe reference fluid

21 Chemical Treatment PLGA films are separated into 7groups with 5 films for each immersed in 2NaOH solutionfor surface hydrolysis for 0min 5min 10min 20min40min 60min and 80min respectively and then washedby deionizedwaterTheir surface contact angles aremeasuredusing a contact angle instrument after drying in fluid nitrogenat room temperature

22 Plasma Treatments The Plasma-Enhanced CVD systemproduced by Japan SANKEN is used in plasma treatmentat the power of 50W and vacuum degree of 20 Pa withthe oxygen as the reactive gas The processes are as followsPLGA films are placed beneath the electrode in the cavitythe vacuum degree is reduced to 10 Pa and then maintainedat 20 Pa after filling with oxygen The glow discharge plasmatreatment could be proceeding between two electrodes byenabling the 50W power 1356MHz alternating currentaccording to the predetermined time For another 10min thefilms are taken out for measurement

23 UV Irradiation Treatment 126 nm and 172 nm UV areused to handle PLGA films and the excimer UV lampis provided by China Jiangsu Youwei Optoelectronics CoLtd Irradiation light is 70W boot time lt1 s illuminatedobject temperature lt40∘C and AC power is 220V50Hz Inthe experiment PLGA films are placed below the excimerUV lamp first then after completing predetermined timeirradiation the films are removed for measurement

24 Measurement and Assessment Contact angle measure-ment Contact Angle Meter (Type OCA20) produced byGermany Dataphysics is used to measure the contact angleby sessile drop method and deionized water as the referencesolutionThe results are recorded by the equipment automat-ically

Bonding strength measurement the tension test is per-formed by America Electron-Tensile Tester (Type 1095) andthe tensile rate is 1mmmin

Interface morphology measurement the films areobserved by Japan Olympus microscope (Type SZX16)

3 Results and Discussion

31 Chemical Treatment Result Figure 2 shows the chemicaltreatment results of the PLGA film Where 119909-axis representstime of chemical treatment 119910-axis represents the value ofthe contact angle From the figure we can see that NaOHtreatment reduces the surface contact angle of the PLGAfilm


0 10 20 30 40 50 60 70 80 900

10

20

30

40

50

60

70

80


Con

tact

angl

e(∘ )


0 5 10 15 20 25 30 350

10

20

30

40

50

60

70

80


Con

tact

angl

e(∘ )





0 50 100 150 200 250 3000

10

20

30

40

50

60

70

80


Con

tact

angl

e(∘ )







0 5 10 15 20 25 30 350

10

20

30

40

50

60

70

80

Time (days)


Con

tact

angl

e(∘ )




35 40 45 50 55 60 65 70 750

1

2

3

4

5

6

7

8

Max

imum

stre

ss (M

Pa)









(a)

(b1) (b2)

(c1) (c2)

200120583m








4 Conclusions




Acknowledgments


References


































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0 10 20 30 40 50 60 70 80 900

10

20

30

40

50

60

70

80


Con

tact

angl

e(∘ )


0 5 10 15 20 25 30 350

10

20

30

40

50

60

70

80


Con

tact

angl

e(∘ )





0 50 100 150 200 250 3000

10

20

30

40

50

60

70

80


Con

tact

angl

e(∘ )







0 5 10 15 20 25 30 350

10

20

30

40

50

60

70

80

Time (days)


Con

tact

angl

e(∘ )




35 40 45 50 55 60 65 70 750

1

2

3

4

5

6

7

8

Max

imum

stre

ss (M

Pa)









(a)

(b1) (b2)

(c1) (c2)

200120583m








4 Conclusions




Acknowledgments


References


































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0 5 10 15 20 25 30 350

10

20

30

40

50

60

70

80

Time (days)


Con

tact

angl

e(∘ )




35 40 45 50 55 60 65 70 750

1

2

3

4

5

6

7

8

Max

imum

stre

ss (M

Pa)









(a)

(b1) (b2)

(c1) (c2)

200120583m








4 Conclusions




Acknowledgments


References


































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a)

(b1) (b2)

(c1) (c2)

200120583m








4 Conclusions




Acknowledgments


References


































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






4 Conclusions




Acknowledgments


References


































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials


















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



research article experiment research on bonding effect of...

Documents