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A Chemocapacitive sensor array for the detection of complex odors

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

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A Chemocapacitive sensor array for the detection of complex odors

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  1. A Chemocapacitive sensor array for the detection of complex odors D. Goustouridis1,2, P. Oikonomou2, A. Botsialas1,2, K. Manoli2, M. Kitsara2, I. Raptis2

  2. Overview • Polymer based gas sensors Principles of operation • Capacitive Polymer Based sensors Methodology for the selection of the Polymers Fabrication of the sensor array • Capacitance measurement set-up Capacitance measurements • Read-out electronics Capacitance measurements • Applied Algorithms Applications • Conclusions – Future Plans 2nd SENS-ERA Workshop, 5-6 Dec. 2012

  3. 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

  4. InterDigitateElectrode (IDE) Capacitive Sensor h Sensitive Layer + - + Electrode Substrate G W λ Top view Side view • Simple and low cost fabrication • Suitable for parallel production • Low power consumption • Promising devices for sensing VOCs or humidity • Could be integrated with read-out electronics 2nd SENS-ERA Workshop, 5-6 Dec. 2012

  5. IDE Chemocapacitor sensing principle Vapor phase h Sorbed molecules + - + Polymer sensitive layer Electrode Substrate λ Change in permittivity of polymer (ΔCε ): i) ΔCε >0, εA(analyte)>εpol(polymer) ii) ΔCε <0, εA(analyte)<εpol(polymer) Capacitance change (ΔC) Sorption of analyte ΔC= f( ΔCε + ΔCh) Swelling of polymer (ΔCh): ΔCh>0 ΔCh~0 if i) h>0.5 λ,ii)εΑ>> εpol for any h 2nd SENS-ERA Workshop, 5-6 Dec. 2012

  6. IDE Chemocapacitor sensing principle Useful Capacitance Electric Field ΔCh: Capacitance change due to swelling ΔCε: Capacitance change due to permittivity change Parasitic Capacitance • Requirements: • Substrate with low dielectric constant (Polymer or Quartz) • Small electrode distance (ideally <1μm) 2nd SENS-ERA Workshop, 5-6 Dec. 2012

  7. IDE Chemocapacitor operating principle Α) Response of chamocapacitor in neutral enviroment, Β) Just before the first sorption Γ) After the sorption, transiet response Δ)Steady response in equilibrium 2nd SENS-ERA Workshop, 5-6 Dec. 2012

  8. 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

  9. Optical Characterization of the polymer swelling Measurement chamber Symbolemtry principle of operation • 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 layer • Fitting (L0) of theoretical spectrum to the measurement one. White Light Reflectance Spectroscopy (WLRS) 2nd SENS-ERA Workshop, 5-6 Dec. 2012

  10. Optical Characterization of the polymer swelling Analyte atmosphere (swelling more) Analyte Atmosphere (swelling) Nitrogen purging Polymer SiO2 Si 2nd SENS-ERA Workshop, 5-6 Dec. 2012

  11. Typical Results Thickness (nm) Time (min) Polymer film: PHEMA Analyte: Humidity Concentrations: 1000-5000-10000-15000-20000 ppm 2nd SENS-ERA Workshop, 5-6 Dec. 2012

  12. Fabrication process of IDC Array Plan view of IDC structure Array of 8 chemopapacitors 2μm electrode – 2μm spacing (die size 7x7mm2) 2nd SENS-ERA Workshop, 5-6 Dec. 2012

  13. Measurement Set-up • Gas delivering unit • Sample’s chamber (volume ~4mm3) • Eight channel matrix switch board (Capacitance meter (HP 4278A) • The set-up is completely controlled by a LabView application Capacitance change (pF) Time(min) 2nd SENS-ERA Workshop, 5-6 Dec. 2012

  14. Measurement set-up 2nd SENS-ERA Workshop, 5-6 Dec. 2012

  15. Response to concentrations of two analytes • Δcdouble.~(ΔCanalyte1+ ΔCanalyte2) • The sensors sense the present or the absent of each analyte. 2nd SENS-ERA Workshop, 5-6 Dec. 2012

  16. Aging through time 4 months later • Good reproducibility and reversibility • Time stability 2nd SENS-ERA Workshop, 5-6 Dec. 2012

  17. Read out & Electronic Module Electronic circuit for up to 8 Chemocapacitance reading 2nd SENS-ERA Workshop, 5-6 Dec. 2012

  18. Typical results of Electronic Module Mesurement of p-xylene(100ppm) with & without Humidity 2nd SENS-ERA Workshop, 5-6 Dec. 2012

  19. PCA analysis Processing of the raw data 2 or 3 axes representation (the most important) Principal Component Analysis (PCA) 2nd SENS-ERA Workshop, 5-6 Dec. 2012

  20. Application I. Wine discrimination 3- Agiorgitiko- red - boutari 4- Naousa-red - boutari Discrimination of white & red wine 1- Limnoswhite dry 2-Moschofilero-white Απόκριση του αισθητήρα PBMA-IDC στα τέσσερα κρασιά για δυο ροές Αποτέλεσμα PCA 2nd SENS-ERA Workshop, 5-6 Dec. 2012

  21. 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

  22. 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

  23. 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

  24. Thank you for your attention E-mail: dgousto@teipir.gr 2nd SENS-ERA Workshop, 5-6 Dec. 2012

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