chemoreceptive neuron mos (c mos) transistors for environmental monitoring: detection in fluid and...
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Chemoreceptive Neuron MOS Chemoreceptive Neuron MOS (C(CMOS) TransistorsMOS) Transistors
for Environmental Monitoring:for Environmental Monitoring: Detection in Fluid and Gas AmbientsDetection in Fluid and Gas Ambients with with Field Programmability and High ReliabilityField Programmability and High Reliability
Edwin C. KanEdwin C. KanSchool of Electrical and Computer EngineeringSchool of Electrical and Computer Engineering
Cornell UniversityCornell University
RD83
22
MotivationMotivation• Silicon-based autonomous
microsystem Sensing abilityCommunicationComputationControl/memory unitsActuation capability Power self-sufficient Ease of manufacture
33
OutlineOutline• CMOS OverviewWhy – Review of literatureWhat – CMOS device structureHow – Device operation
Conclusion
Sensors Fluid ambient (Na+, K+ , Ca2+, BSA and
SDS) Gas ambient (CO2) Readout circuits
Actuators
44
Literature Review (1/3)Literature Review (1/3)
• FET-based (Bergveld 1970)Materials in
contact with silicon oxide
pH sensitiveMany spin-offs
P. Bergveld, Sensors and Actuators B 88, 1 (2003).
ChemFETENFET
(Enzyme) IMMUNOFET
55
Tune resistivity in the sensing scheme
Gardner (1991)Lewis (1996):
electronic noseAdvantage:
sensitivity from tunneling distance modulation
Resistive-based
Literature Review (2/3)Literature Review (2/3)
66
Grimshaw (1990) Lang (1999)
Literature Review (3/3)Literature Review (3/3)
Yamamoto (1987) Steiner (1995)
Chemomechanical
Chemicapacitive
SAW-IDT (Inter-Digital Transducers)Wenzel (1990) Nakamoto (1991)
Dong, et al., Sensors and Actuators B76, 130 (2001).
77
Why CWhy CMOS?MOS?• Integrated device structure for sensors
• Enhancement of DOFs in sensing
• Ease of integration with current CMOS technology
• Charge-based operation to reduce power consumption
• Potential for sensor-array application
• Possibility to integrated sensors and actuators with the same structure
88
CCMOS ObjectivesMOS Objectives
• High sensitivity
• High selectivity
• Reproducibility, stability and reliability
• Simple calibration and reset protocols
• Field reconfigurability
• Versatile transient measurement
• Low power consumption in the system
• Low manufacturing cost
99
CCMOS Device StructureMOS Device Structure
• Extended floating gate
MOSFETMOSFET
Only one sensing gate is used at the current stage
Drain
Floating Gate
Control Gate
Source
Insulation Structure
Sensing Gates
1010
Polymer-Coating ParametersPolymer-Coating Parameters
Polymer Coating SolutionMolecular Weight
poly(vinyl acetate) 20 mg in 10 mL Tetrahydrofuran 90,000
poly(vinyl butyral) 20 mg in 10 mL Tetrahydrofuran 100,000150,000
poly(ethylene -co- vinyl acetate) 100 mg in 10 mL Benzene 72:28 (wt.)
poly(vinyl chloride) 20 mg in 10 mL Tetrahydrofuran 110,000
Polymer CoatingThickness
(nm)Roughness
Ra (nm)Roughness
Rq (nm)
poly(vinyl acetate) 50 64 88
poly(vinyl butyral) 25 20 27
poly(ethylene -co- vinyl acetate) 30 2 2
poly(vinyl chloride) 30 8 13
1111
Dip-Pen TechnologyDip-Pen Technology
D. Piner, J. Zhu, F. Xu, and S. Hong, C. A. Mirkin, Science 283, 661 (1999).
Molecules delivered from the AFM tip to solid substrate via capillary transport
30-nm linewidth resolution
• For smaller sensing gates
1212
Microfluidic ChannelsMicrofluidic Channels
• Close-up views
Contact Openings
Channels
Fluid Delivery Opening
Channel
Devices
ProbesContact Pads
Contact Openings: Epoxy 907 @ 60 °C for 2 hours
1313
OutlineOutline
• Development of the chemoreceptive neuron MOS (CMOS) trasistorsDevice operations and results
Sensors Actuators
1414
Device OperationDevice Operation• Record initial device I-V characteristics
• Apply polymer coating and insulation elastomer
• Deliver fluid to the microfluidic channel (base buffer, electrolytes, or buffer loaded with protein molecules)
• Observe and record changes in threshold voltages (Vt)
and subthreshold slopes (S): extract CSG and OHP
• Electron-tunneling operation: apply bias (30V or -30V for 50 seconds) at the control gate
• Observe and record Vt and S
• Perform cleansing steps (e.g. rinsing, N2 drying)
• Re-align insulation layer and repeat I-V measurements
1515
Phenomena at the InterfacePhenomena at the Interface• GCS model
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-
-
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-
-
-
-
-
Solid/Liquid Interface
IHP OHP
Diffuse Layer
Specifically Adsorbed Ion
Solvated Ions
-
-
-
+
+
+
+
+
+
+
+
+
Solvent molecule
-
-
-
-
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-
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Solid/Liquid Interface
IHP OHP
Diffuse Layer
Specifically Adsorbed Ion
Solvated Ions
--
--
--
++
++
++
++
++
++
++
++
++
Solvent molecule
Double-layer capacitanceDouble-layer capacitance
CCHH: Helmholtz-plane capacitance: Helmholtz-plane capacitance
CCDIFDIF: Diffuse-layer capacitance: Diffuse-layer capacitance
zz: magnitude of the charge on the ions: magnitude of the charge on the ionsnn: concentration of the ions : concentration of the ions OHPOHP: potential at the OHP: potential at the OHP
DIFHEDL CCC
111
dAx
CSGA
OHP
rH
0
0
SGAOHPr
DIF dAkT
zq
kT
nqzC
0
21220
2cosh
2
xxOHPOHP: dist. between : dist. between
Helmholtz planesHelmholtz planes
1616
Capacitive-Divider ModelCapacitive-Divider Model
)(0TDTSTFG UVUVUV eeeII
Subthreshold Subthreshold current modelcurrent model
SlopeSlope
SGCGgdgsbdepoxT CCCCCCCC )//( Changed by fluidsChanged by fluids
D
T
gd
S
T
gs
T
T VC
CV
C
C
C
QV
Above-threshold Above-threshold voltage-shift modelvoltage-shift model
SG
T
SGCG
T
CGD
T
gd
S
T
gs
T
FG VC
CV
C
CV
C
CV
C
C
C
QV
)( depoxox CCC
EDL capacitanceCCG
VCG
CSGCox
Cdepl
Cgd
VD
Cgd
VD
Cgs
VS
Cgs
VS
Cb
QVFG
1717
Sample IV IllustrationSample IV Illustration
1E-13
1E-12
1E-11
1E-10
1E-09
1E-08
1E-07
1E-06
1E-05
1E-04
1E-03
-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10
Control Gate Voltage (V)
Dra
in C
urre
nt (A
)
W channelW DI waterW elec. outW 72 hours
Sc
Sm
So
10-3
10-4
10-5
10-6
10-7
10-8
10-9
10-10
10-11
10-12
10-13
Dra
in C
urre
nt (
A)
10-3
10-4
10-5
10-6
10-7
10-8
10-9
10-10
10-11
10-12
10-13
Dra
in C
urre
nt (
A)
DI Water on Polysilicon
St
2
1
3
cc : after applying : after applying insulation elastomer insulation elastomer with microfluidic with microfluidic channelschannels
mm : after delivering : after delivering the sample fluidthe sample fluid
oo : after tunneling : after tunneling electrons out of the electrons out of the floating gatefloating gate
tt : after cleansing : after cleansing steps and a period of steps and a period of time in the dry box time in the dry box with constant Nwith constant N22 flow flow
Notations:Notations:
1818
Sensing-Gate ResponsesSensing-Gate Responses• Influence from the fluid Induce image charge at the extended floating gate Modify series capacitance to the sensing gate Affect floating-gate potential and total capacitive load;
create distinctive threshold-voltage shifts and subthreshold-slope variations
• Capacitance indication Collect information via capacitive coupling from the fluid
bulk to the extended floating-gate structure Detect variations before and after electron-tunneling
operations
1919
Subthreshold SlopesSubthreshold Slopes
)(0TDTSTFG UVUVUV eeeII
SG
T
SGCG
T
CGD
T
gd
S
T
gs
T
FG VC
CV
C
CV
C
CV
C
C
C
QV
CG
TT
C
CUS
10ln
1
10 )(log
CGV
IS
SGCGgdgsbdepoxT CCCCCCCC )//(
1E-13
1E-12
1E-11
1E-10
1E-09
1E-08
1E-07
1E-06
1E-05
1E-04
1E-03
-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10
Control Gate Voltage (V)
Dra
in C
urre
nt (A
)
W channelW DI waterW elec. outW 72 hours
Sc
Sm
So
10-3
10-4
10-5
10-6
10-7
10-8
10-9
10-10
10-11
10-12
10-13
Dra
in C
urre
nt (
A)
10-3
10-4
10-5
10-6
10-7
10-8
10-9
10-10
10-11
10-12
10-13
Dra
in C
urre
nt (
A)
DI Water on Polysilicon
St
2
1
3
Extraction Extraction of of S S valuesvalues
2020
Data AnalysesData Analyses• Extraction of subthreshold slopes from the
measured I-V recordings• Direct estimation of sensing-gate
capacitance (CSG), eliminating control-gate capacitance (CCG) variation
pprSGrr
SG CCCS
SC
1
1
10lnTU
CGT CSC
SGCGpT CCCC
gdgsbdepoxp CCCCCC )//(
2121
Reference Reference SSrr
Notations:Notations:
5 mM KCl d1r d1c d1m d1i d1t d2r d2c d2m d2i d2t
polysilicon 148 177 553 728 166 200 213 771 1019 217
poly(vinyl acetate) 187 198 270 272 194 284 296 435 455 293
poly(vinyl butyral) 228 231 687 985 228 160 176 663 830 165
poly(ethylene -co- vinyl acetate)
163 197 673 711 180 156 183 575 668 166
poly(vinyl chloride) 288 301 469 491 279 212 215 1164 1308 219
d1, d2 d1, d2 : device 1, device 2: device 1, device 2
r r : initial reference: initial reference
c c : after channel formation: after channel formation
m m : after fluid delivery: after fluid delivery
ii : electron tunneling in, 30 V, 50 s. : electron tunneling in, 30 V, 50 s.
t t : recordings after cleansing steps : recordings after cleansing steps and a period of time in the dry boxand a period of time in the dry box
Normalization required to get Normalization required to get rid of the fabrication variation rid of the fabrication variation
2222
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
1 2 3
Sample Fluids
d1i-
m N
orm
polysiliconpoly(vinyl acetate)poly(vinyl butyral)poly(ethylene -co- vinyl acetate)poly(vinyl chloride)
DI water 0.005M NaCl 0.005M KCl
After electron tunneling
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
1 2 3
Sample Fluids
d1m
-c N
orm
polysiliconpoly(vinyl acetate)poly(vinyl butyral)poly(ethylene -co- vinyl acetate)poly(vinyl chloride)
DI water 0.005M NaCl 0.005M KCl
Before electron tunneling
Normalized Normalized CCSGSG
Before electron injectionBefore electron injection After electron injectionAfter electron injection
““Discernible patterns”Discernible patterns”
CS
G
CS
G
Variation by polymers Variation by polymers Difference between fluidsDifference between fluids
(√)(√)
(X)(X)
2323
0.0
0.5
1.0
1.5
2.0
2.5
3.0
1 2 3
Sample Fluids
Sel.
01 d
2i-m
Nor
m
polysiliconpoly(vinyl acetate)poly(vinyl butyral)poly(ethylene -co- vinyl acetate)poly(vinyl chloride)
Mixture 0.5M NaCl 0.05M KCl0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
11.0
12.0
1 2 3
Sample Fluids
Sel.
01 d
2m-c
Nor
m
polysiliconpoly(vinyl acetate)poly(vinyl butyral)poly(ethylene -co- vinyl acetate)poly(vinyl chloride)
Mixture 0.5M NaCl 0.05M KCl
Selectivity Demonstration (1/2)Selectivity Demonstration (1/2)
Before electron injectionBefore electron injection
““Difference not obvious”Difference not obvious”
After electron injectionAfter electron injection
““Discernible patterns”Discernible patterns”
Mixture contains both solutions in corresponding concentrationMixture contains both solutions in corresponding concentrationC
SG
CS
G
2424
Selectivity Demonstration (2/2)Selectivity Demonstration (2/2)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
1 2 3
Sample Fluids
Sel
. 01
d2i-
m N
orm
polysiliconpoly(vinyl acetate)poly(vinyl butyral)poly(ethylene -co- vinyl acetate)poly(vinyl chloride)
Mixture 0.5M NaCl 0.05M KCl
CS
G
Additive or subtractive responses in the sensor-array plots
• Sensor-array plots
0.0
2.51
2
34
5
Mixture
0.5 M NaCl
0.05 M KCl
2525
Double-Layer Parameters (1/3)Double-Layer Parameters (1/3)
Cdif
(F/cm2)DI
Water
NaCl Solution KCl Solution
50 0.005M 0.05M 0.5M 50 0.005M 0.05M0.5M
polysilicon 6.4 7.0 7.5 19.3 26.0 5.7 4.9 4.0 4.0
poly(vinyl acetate) 20.1 1.7 7.5 8.3 114.5 6.6 7.6 74.6 15.0
poly(vinyl butyral) 1.8 6.0 13.2 16.4 33.6 4.8 4.3 3.3 4.0
poly(ethylene -co- vinyl acetate)
1.2 8.9 67.7 105.1 9.9 9.0 0.9 1.3 2.3
poly(vinyl chloride) 1.1 2.1 3.2 8.3 20.6 0.4 2.4 26.6 14.9
Cdif from extracted S
pprSGrr
SG CCCS
SC
1
1
10lnTU
CG
TT
C
CUS
10ln
2626
Double-Layer Parameters (2/3)Double-Layer Parameters (2/3)• Extracted OHP (before elec. injection)
Nernst Equation
0
50
100
150
200
250
300
350
400
0 1 2 3 4 5
Concentration
d2 P
hi_O
HP
(m
V)
Slope ~ 60 mV/decadeSlope ~ 60 mV/decade
50M 0.005M 0.05M 0.5M500M
OH
P(m
V)
for
d2
DI water
NaCl on 5 surfacesKCl on 5 surfacesDI Water on 5 surfaces
NaCl on 5 surfacesKCl on 5 surfacesDI Water on 5 surfaces
Rd
Ox
C
C
nF
RTEE ln0
RdneOx RT/F = kT/q
~ 25.9 mV at room temp.
OHP decreases at ~ 60 mV/dec. with increases in concentration
2727
Double-Layer Parameters (3/3)Double-Layer Parameters (3/3)
0
20
40
60
80
100
120
0 1 2 3 4 5
Concentration
d1 D
Phi_
OH
P (m
V)
NaCl
KCl
DI Water
50M 0.005M 0.05M 0.5M500MDI water
Surface: Polysilicon
Increasing along concentration
O
HP
(mV
)
d1
0
20
40
60
80
100
120
0 1 2 3 4 5
Concentrationd2
DPh
i_O
HP
(mV
)
NaCl
KCl
DI Water
50M 0.005M 0.05M 0.5M500MDI water
Surface: Poly(vinyl butyral)
O
HP
(mV
)
d2 Increasing along
concentration
The change of the The change of the OHPOHP
increases with increasing increases with increasing concentration in NaClconcentration in NaCl
For KCl solution, no For KCl solution, no significant increasing trend significant increasing trend
is observed as in NaClis observed as in NaCl
OHP (after electron injection)
Surface: Polysilicon Surface: Poly(vinyl butyral)
2828
Detection in Gas AmbientsDetection in Gas Ambients
2929
Gate Voltage (V)
-10 -5 0 5 10
Dra
in C
urr
ent
(A)
10-14
10-13
10-12
10-11
10-10
10-9
10-8
10-7
10-6
10-5
10-4
10-3
SDS (Uncharged)SDS (Charged)BSA (Uncharged)BSA (Charged)Lysozyme (Uncharged)Lysozyme (Charged)
Protein SensingProtein Sensing
BSA: bovine serum albumin SDS: sodium dodecyl sulfate
3030
CMOS Circuit CMOS Circuit IntegrationIntegration
CG1
TT
/
/
CG1
TTd
10
1
12s
Lin
sHin
C
CUlnS
e
eln
C
CUV
II
II
MOSIS AMI foundry fabrication (April 2004)
Current mirrors
DC bias current for power/freq tradeoffs
Sample and hold
Control/clock
Vd readout
Vs readout
3131
Sample-and-Hold Control SignalSample-and-Hold Control Signal
Control signal for sample and hold in the readout circuits (monitoring signals from measurement)
3232
Readout CalibrationReadout Calibration
Quasi-static operations with reliable resets
3333
Readout ChannelReadout Channel
3434
OutlineOutline
• Development of the chemoreceptive neuron MOS (CMOS) trasistorsDevice operations and results
Sensors Actuators
3535
Electrowetting ActuationElectrowetting Actuation
• Conventional approach – the change of surface tension at the solid-liquid interface by directly applying different voltages
• Young’s equation
• Lippman’s equation
cosgssg
200 2VV
Cedlslsl
2
0lg
0 2cosarccos VV
Cedl
lg
s
gsl
sgsl
lgLiquid Air Solid
3636
Device StructuresDevice Structures
Microfluidic channel only Microfluidic channel only partially covered to avoid air partially covered to avoid air pressure against actuation pressure against actuation
Transparent elastomer layer Transparent elastomer layer provides easy observation provides easy observation of the saline-water actuationof the saline-water actuation
Device Type 1
Insulation elastomer layer
Silicon substrate
Extended floating gate
Field oxide
Actuation surface layer
Channel oxide
Reference voltage
Control oxide
Device Type 2
Silicon substrate
Active area
Control oxide
Field oxide
Channel oxide Actuation
surface
Extended floating gate
Insulation elastomer layer
3737
Equilibrium in the ChannelEquilibrium in the Channel
- - - - - - - - -- - - - - - - - -- - - - - - - - -- - - - - - - - -InterfaceIHP
OHP
Diffuse Layer
Specifically Adsorbed Ion
Solvated Ions
-- ---
++ ++ ++ ++++
++ ++
++++
Solvent molecule
- - - - - - - - -- - - - - - - - -- - - - - - - - -- - - - - - - - -InterfaceIHP
OHP ++ ++ ++ ++++
-- - --- --
sg
Air
Solid
lg
sl
Solid
Liquid
3838
Actuation SchemeActuation Scheme
Fluid Reservoir
Fluid Reservoir
Aligned insulation elastomer layer
Source
Drain
Control gates
to Vref
Floating-gate extension
Drain
Source
Source
Drain
Drain
SourceControl gates
3939
Result IllustrationsResult Illustrations
Liquid front advances about Liquid front advances about 10 10 m after electrons are m after electrons are tunneled to the floating gate tunneled to the floating gate
Less change in equilibrium Less change in equilibrium liquid length for the wider liquid length for the wider channel after actuationchannel after actuation
Device Type 2 Beforeelectron injection
Afterelectron injection
Embedded active area for reference voltage
Actuation surface
10m
Trapped air bubble
~5m
Floating gate underneath actuation surface
Channel width
Metal connection to reference voltage
Device #1
~10mLiquid front
advancingEmpty channel segment (no liquid)
Before electron injection
After electron injection
20m
Type 1
4040
Control ExperimentsControl Experiments
connection to ground
connection to ramping voltage
Channel width
20m
~10m
Liquid front advancing
Control test #1
Control test #2
Initial condition After 30 minutes
Unaltered liquid front
Asymmetrical liquid-front Asymmetrical liquid-front advancing by directly advancing by directly sweeping external voltages sweeping external voltages
Equilibrium length of the Equilibrium length of the liquid almost unchanged liquid almost unchanged after 30 minutesafter 30 minutes
4141
Electrowetting on CElectrowetting on CMOSMOS• Modification of interfacial charges results in the
change in solid-liquid interfacial tension and hence the equilibrium length of the liquid in the microfluidic channel
• Potential for integration with the CMOS sensors and conventional CMOS circuitry for fluid delivery
• Air-trapping considerations for further device designs in microfluidic application
• No actuation observed for KCl solution; results agree with OHP after elec. injection
4242
Selective to Buffer SpeciesSelective to Buffer Species
0
20
40
60
80
100
120
0 1 2 3 4 5
Concentration
d1 D
Phi_
OH
P (m
V)
NaCl
KCl
DI Water
50M 0.005M 0.05M 0.5M500MDI water
Surface: Polysilicon
Increasing along concentration
O
HP
(mV
)
d1
0
20
40
60
80
100
120
0 1 2 3 4 5
Concentrationd2
DPh
i_O
HP
(mV
)
NaCl
KCl
DI Water
50M 0.005M 0.05M 0.5M500MDI water
Surface: Poly(vinyl butyral)
O
HP
(mV
)
d2 Increasing along
concentration
The change of the The change of the OHPOHP
increases with increasing increases with increasing concentration in NaClconcentration in NaCl
For KCl solution, no For KCl solution, no significant increasing trend significant increasing trend
is observed as in NaClis observed as in NaCl
OHP (after electron injection)Surface: Polysilicon Surface: Poly(vinyl
butyral)
4343
Smart Sensors and ActuatorsSmart Sensors and Actuators
A
A
AS S
S SS
Applicable surface coatings on sensors and/or actuators
A
A
AS S
S SS
Applicable surface coatings on sensors and/or actuators
Controlled fluid delivery for more reliable sensing
Analysis/feedback circuitry from CMOS to provide fluid information (variety, position, etc.)
Various surface coatings individually applied on sensors and/or actuators
4444
OutlineOutline
• Development of the chemoreceptive neuron MOS (CMOS) trasistors
• Summary and future directions
Why – Review of literatureWhat – CMOS device structureHow – Device operation
SensorsActuators
4545
Summary (1/2)Summary (1/2)
• FET devices with extended floating gates for chemical sensing
• Floating-gate structure for electron-tunneling operations provides more DOFs for sensing
• Indicators from I-V characteristics: Subthreshold slopes (S) and threshold voltages (Vt)
• CMOS integration enables detailed control circuits
4646
Summary (2/2)Summary (2/2)
• Normalized CSG in the polymeric responses directly couples to subthreshold slopes and the patterns encourage sensor-array application in the lock-and-key implementation
• Electrowetting actuator for potential microvalves integrated with the sensors and conventional CMOS circuitry for fluid delivery and confinement