A Chemocapacitive sensor array for the detection of complex odors D. Goustouridis 1,2, P. Oikonomou...

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)


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


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


IDE Chemocapacitor sensing principle


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





Time

Capa

cita

nce

(pF)

Β

Γ

Δ

A B

Δ


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


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.


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)


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)


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)


Fabrication process of IDC Array

Array of 8 chemopapacitors2μm electrode – 2μm spacing(die size 7x7mm2)

Plan view of IDC structure


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


Measurement set-up


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)


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


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


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


PCA analysis

Principal Component Analysis (PCA)

Processing of the raw data2 or 3 axes representation(the most important)


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


Application II: Fragmentation monitoring

Response of 2 IDC vs time

Fragmentation vs time according to PCA analysis


-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


Future plans

Δίκτυο• Development of submicron IDCs.• Apply pattern recognition algorithms• Implementation of a wireless network• Measurements in real environment.


Thank you for your attention

E-mail: [email protected]


Date post:	27-Mar-2015
Category:	Documents
Upload:	steven-willis
View:	212 times
Download:	0 times

A Chemocapacitive sensor array for the detection of complex odors D. Goustouridis 1,2, P. Oikonomou...

Documents