a chemocapacitive sensor array for the detection of complex odors
DESCRIPTION
A Chemocapacitive sensor array for the detection of complex odors. D. Goustouridis 1,2 , P. Oikonomou 2 , A. Botsialas 1,2 , K. Manoli 2 , M. Kitsara 2 , I. Raptis 2. Overview. Polymer based gas sensors Principles of operation Capacitive Polymer Based sensors - PowerPoint PPT PresentationTRANSCRIPT
A Chemocapacitive sensor array for A Chemocapacitive sensor array for the detection of complex odorsthe detection of complex odors
D. Goustouridis1,2, P. Oikonomou2, A. Botsialas1,2, K. Manoli2, M. Kitsara2, I. Raptis2
1. Department of ElectronicsTEI PiraeusE-mail: [email protected]
2. Inst. Of MicroelectronicsNCSR “Demokritos”
2nd SENS-ERA Workshop, 5-6 Dec. 2012
Overview
Polymer based gas sensorsPolymer based gas sensorsPrinciples of operation
Capacitive Polymer Based sensorsCapacitive Polymer Based sensorsMethodology for the selection of the PolymersFabrication of the sensor array
Capacitance measurement set-upCapacitance measurement set-upCapacitance measurements
Read-out electronicsRead-out electronicsCapacitance measurements
Applied AlgorithmsApplied AlgorithmsApplications
Conclusions – Future PlansConclusions – Future Plans
Chemical sensors
Piezoelectic (surface acoustic waves SAW, bulk acoustic waves BAW, cantilever resonator)
Optical (fluorescence, reflective, absorption)
Thermal (pellistor)
Electrical, Electrochemical ( chemoresistive, MOX, chemocapacitive)
2nd SENS-ERA Workshop, 5-6 Dec. 2012
Simple and low cost fabricationSimple and low cost fabrication Suitable for parallel productionSuitable for parallel production Low power consumptionLow power consumption Promising devices for sensing VOCs or humidityPromising devices for sensing VOCs or humidity Could be integrated with read-out electronicsCould be integrated with read-out electronics
+ - +Electrode
Sensitive Layer
Substrate
λ
h
WG
Top view Side view
InterDigitateElectrode (IDE) Capacitive Sensor
2nd SENS-ERA Workshop, 5-6 Dec. 2012
Sorbed molecules
+ - +
Vapor phase
Electrode Polymersensitive layer
Substrate
λ
h
ΔC= f( ΔCε + ΔCh)Sorption of
analyte
Change in permittivity of polymer (ΔCε ):i) ΔCε >0, εA(analyte)>εpol(polymer)ii) ΔCε <0, εA(analyte)<εpol(polymer)
Swelling of polymer (ΔCh): ΔCh>0ΔCh~0 if i) h>0.5 λ, ii) εΑ>> εpol for any h
Capacitance change (ΔC)
IDE Chemocapacitor sensing principle
2nd SENS-ERA Workshop, 5-6 Dec. 2012
IDE Chemocapacitor sensing principle
2nd SENS-ERA Workshop, 5-6 Dec. 2012
Electric Field Useful Capacitance
Parasitic Capacitance
Requirements:Substrate with low dielectric constant (Polymer or Quartz)Small electrode distance (ideally <1μm)
ΔCε: Capacitance change due to permittivity change
ΔCh: Capacitance change due to swelling
IDE Chemocapacitor operating principle
+ - +Sensitive Layer
Insulating Substrate
+ - +Sensitive Layer
Insulating Substrate
+ - +Sensitive Layer
Insulating Substrate
Time
Capa
cita
nce
(pF)
Β
Γ
Δ
A B
Δ
+ - +Sensitive Layer
Insulating SubstrateA
Γ
Α) Response of chamocapacitor in neutral enviroment,Β) Just before the first sorptionΓ) After the sorption, transiet responseΔ) Steady response in equilibrium
2nd SENS-ERA Workshop, 5-6 Dec. 2012
Development of an e-nose
Choosing of the polymers for gas sorption Choosing of group of polymer (according to specific application)
(Compatibility with the measuring gases, chemical affinity, technological issues, …)
Control of sorption – desorption, repeatability, selectivity Transducer & Sensor Development
Deposition techniques Implementation of Interdigitated Electrodes & characterization.
Read-Out electronics Development of read-out electronics and data transmittion modules
Development of Data processing algorithms Application of raw data processing algorithms for the identification of the
gas composition.
2nd SENS-ERA Workshop, 5-6 Dec. 2012
Optical Characterization of the polymer swelling
Measurementchamber
Symbolemtry principle of operation
)(4
cos4
cos4
cos 00111
10
0 LnLnDLnCL
nBAEo
The energy E at wavelength λ is (for the case of single layer film):
n : Refractive index, L: thickness, λ: wavelength.με 0: πολυμερές 1:.0 indicates the polymer layer & 1 the SiO2 layerFitting (L0) of theoretical spectrum to the measurement one.
White Light Reflectance Spectroscopy (WLRS)
2nd SENS-ERA Workshop, 5-6 Dec. 2012
Optical Characterization of the polymer swelling
Polymer
SiO2
Si
Nitrogen purgingAnalyte Atmosphere
(swelling)
Analyte atmosphere(swelling more)
500 600 700 800 9000
500
1000
1500
2000
2500
3000
Refl
ecta
nce
Sig
nal (
a.u.
)
wavelnegth (nm)
600 610 620 630
2800
2900
3000
3100
Refl
ecta
nce
Sig
nal (
a.u.
)
wavelnegth (nm)
2nd SENS-ERA Workshop, 5-6 Dec. 2012
Typical Results
Polymer film: PHEMA Analyte: Humidity Concentrations: 1000-5000-10000-15000-20000 ppm
450 500 550 600 650 700 750 800 85092
93
94
95
96
97
98
9920000 ppm
15000 ppm
10000 ppm
5000 ppm
Χρόνος ( min)
PHEMA - Υγρασία
1000 ppm
Time (min)
2nd SENS-ERA Workshop, 5-6 Dec. 2012
Fabrication process of IDC Array
Array of 8 chemopapacitors2μm electrode – 2μm spacing(die size 7x7mm2)
Plan view of IDC structure
2nd SENS-ERA Workshop, 5-6 Dec. 2012
Measurement Set-up
Time(min)Ca
pac
itan
ce c
ha
nge
(p
F)1. Gas delivering unit 2. Sample’s chamber (volume
~4mm3)3. Eight channel matrix switch board
(Capacitance meter (HP 4278A)4. The set-up is completely
controlled by a LabView application
2nd SENS-ERA Workshop, 5-6 Dec. 2012
Measurement set-up
2nd SENS-ERA Workshop, 5-6 Dec. 2012
Response to concentrations of two analytes
Δcdouble.~(ΔCanalyte1+ ΔCanalyte2) The sensors sense the present or the absent of each analyte.
20 40 60 80 100 120 140 160 180
0.0
0.3
0.6
0.9
1.2
PBMA with initial Capacitance CP= 11pF
-EtOH
-H2O H
2O+EtOH
-AcOOEt
-AcOOEt
-H2O -EtOH
H2O+AcOOEt
AcOOEt+EtOH
Capacitance C
hange
C(p
F)
Time(min)
2nd SENS-ERA Workshop, 5-6 Dec. 2012
Aging through time
4 months later
0 50 100 150 200
48.6
48.8
49.0
49.2
49.4
70
72
74
76
78
80
5000ppm H2O
Cap
acita
nce
(pF)
Time(min)
PHEMAPBMA
5000ppm AcOOEt
Good reproducibility and reversibility
Time stability
0 50 100 150 200
48.0
48.2
48.4
48.6
70
72
74
76
78
80
5000ppm H2O
Capaci
tance
(pF)
Time(min)
PHEMAPBMA
5000ppm AcOOEt
2nd SENS-ERA Workshop, 5-6 Dec. 2012
Read out & Electronic ModuleElectronic circuit for up to 8 Chemocapacitance reading
PC USB to I2C Converter
8-BIT I/O Expander
AD7746
(8:1)x2 Analog Multiplexer
8 Capacitive Sensor Array
I2C Bus
MUX In
MUX Control Signals
MUX Out
USB
2nd SENS-ERA Workshop, 5-6 Dec. 2012
Typical results of Electronic Module
0 100 200 300 400 500 600
0
20
40
60
80
100
120
140
160
180
200
capac
itan
ce c
han
ge C
(fF)
p-xylene 100ppmexposure
50% relative humidity
mixture
removal
p-xylene
PBMA
0
1000
2000
3000
4000
5000
PHEMA
Mesurement of p-xylene(100ppm) with & without Humidity
2nd SENS-ERA Workshop, 5-6 Dec. 2012
PCA analysis
Principal Component Analysis (PCA)
Processing of the raw data2 or 3 axes representation(the most important)
2nd SENS-ERA Workshop, 5-6 Dec. 2012
Application I. Wine discriminationDiscrimination of white & red wine1- Limnos white dry2-Moschofilero-white
0 1800 3600 5400 7200 9000 1080051.3
51.4
51.5
51.6
51.7
51.8
51.9
52.0
Time (min)
PBMA
Cap
acitan
ce C
han
ge C
(pF)
Απόκριση του αισθητήρα PBMA-IDC στα τέσσερα κρασιά για δυο ροές
Αποτέλεσμα PCA-2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5
0.0
0.5
1.0
1.5
PC
1
PC2
3- Agiorgitiko- red - boutari4- Naousa-red - boutari
2nd SENS-ERA Workshop, 5-6 Dec. 2012
Application II: Fragmentation monitoring
Response of 2 IDC vs time
Fragmentation vs time according to PCA analysis
2nd SENS-ERA Workshop, 5-6 Dec. 2012
-3 0 3
-4
-2
0
2
4
1 (v/v EtOH) 2 (0.34%) 3 (3.4% ) 4 (7.12% ) 5 (10.36%) 6 (12.04% ) 7 (12.9% ) 8 (12.9% )
2 (v/v EtOH) 1 (0.34%) 2 (0.34%) 3 (0.34%) 4 (2.36%) 5 (6.34%) 6 (9.54%) 7 (12.04%) 8 (12.9%) 9 (12.9%)
4% (v/v) 6% (v/v) 8% (v/v) 10% (v/v) 12% (v/v)
PC
2
PC1
Musts 1& 2
Wines 1 & 2
Ethanol standards
Conclusions
• Methodology Development of Methodology for the characterization of polymer based
chemocapacitors• Polymeric Films Characterization of polymers films for odors sensing• Chemocapacitors Array Development of implementation techniques of chemocapacitos Implementation & characterization of chemocapacitos Array• Read out electronics Development of a hybrid system of chemocapacitors array with appropriate read-
out electronics• Λογισμικό ανίχνευσης αερίων Λογισμικό PCA• Εφαρμογές
Ζύμωση γλεύκους
2nd SENS-ERA Workshop, 5-6 Dec. 2012
Future plans
Δίκτυο• Development of submicron IDCs.• Apply pattern recognition algorithms• Implementation of a wireless network• Measurements in real environment.
2nd SENS-ERA Workshop, 5-6 Dec. 2012