Flexible sensorial system based on capacitive chemical sensors integrated with readout circuits fully fabricated on ultra thin substrate

Abstract In this paper we present the design and fabrication of a fully flexible sensorial system, composed of three different sensor units implemented on an ultrathin polyimide substrate of 8 μm thick. Each unit is composed by a capacitive chemical sensor integrated with readout electronics. The sensors are parallel plate capacitors with the top electrode properly patterned to allow analytes diffusion into the dielectric that acts as chemical interactive material. Three different polymers, poly(tetrafluoroethene) (PTFE), poly(methyl 2-methylpropenoate) (PMMA) and benzocyclobutene (BCB), were used as dielectrics. A ring oscillator circuit, implemented with polysilicon thin film transistors (PS-nTFT), was used to convert the capacitance variations into frequency shifts. The electronic tests show oscillating frequencies of about 211 ± 2 kHz and negligible frequency shifts under different bending radius conditions. Furthermore, system response to some alcohols concentrations (Methanol, ethanol, 1-butanol, and 1-propanol) is reported and data analysis proves that the system is able to discriminate methanol from ethanol.

[1]  M. Martí,et al.  Electronic noses in the quality control of alcoholic beverages , 2005 .

[2]  Ching-Liang Dai,et al.  Capacitive Micro Pressure Sensor Integrated with a Ring Oscillator Circuit on Chip , 2009, Sensors.

[3]  Jérôme Courbat,et al.  Temperature, humidity and gas sensors integrated on plastic foil for low power applications , 2009 .

[4]  N. Donato,et al.  Capacitive humidity sensors based on MWCNTs/polyelectrolyte interfaces deposited on flexible substrates , 2009, Microelectron. J..

[5]  Flexible Glucose Sensor Using Biocompatible Polymers , 2006, 2006 5th IEEE Conference on Sensors.

[6]  Z. Suo,et al.  Mechanics of rollable and foldable film-on-foil electronics , 1999 .

[7]  Luca Maiolo,et al.  Low-temperature polysilicon thin film transistors on polyimide substrates for electronics on plastic , 2008 .

[8]  Antonella Macagnano,et al.  Design and optimization of an ultra thin flexible capacitive humidity sensor , 2009 .

[9]  L. Colalongo,et al.  Floating body effects in polysilicon thin-film transistors , 1997 .

[10]  Herbert Lifka,et al.  58.4: Invited Paper: Flexible Displays and Electronics Made in AM‐LCD Facilities by the EPLaR™ Process , 2007 .

[11]  Z. Ignjatovic,et al.  An interface circuit for measuring capacitance changes based upon capacitance-to-duty cycle (CDC) converter , 2005, IEEE Sensors Journal.

[12]  Bo Wang,et al.  High-accuracy circuits for on-chip capacitive ratio testing and sensor readout , 1998, IEEE Trans. Instrum. Meas..

[13]  N. Niklasch,et al.  New digital readout electronics for capacitive sensors by the example of micro-machined gyroscopes , 2002 .

[14]  Bedrich J. Hosticka,et al.  A novel readout technique for capacitive gas sensors , 1990 .

[15]  Fabrice Axisa,et al.  Flexible technologies and smart clothing for citizen medicine, home healthcare, and disease prevention , 2005, IEEE Transactions on Information Technology in Biomedicine.

[16]  J W Gardner and P N Bartlett,et al.  Electronic Noses: Principles and Applications , 1999 .

[17]  I. Jolliffe.  Principal Component Analysis , 2002 .

[18]  Magni Martens,et al.  Application of an electronic nose system for prediction of sensory quality changes of a meat product (pizza topping) during storage , 2007 .

[19]  J. Bosset,et al.  The electronic nose applied to dairy products: a review , 2003 .

[20]  Jun Wang,et al.  Discrimination of LongJing green-tea grade by electronic nose , 2007 .

[21]  Jérôme Courbat,et al.  Reversed processing of dry photoresist: application to the encapsulation of chemical sensors , 2010 .

[22]  Todd E. Mlsna,et al.  Chemicapacitive Microsensors for Chemical Warfare Agent and Toxic Industrial Chemical Detection , 2006 .

[23]  Andrea Scorzoni,et al.  Flexible tag microlab development: Gas sensors integration in RFID flexible tags for food logistic , 2007 .

[24]  Seongjeen Kim.  Flexible Alcohol Vapor Sensors Using Multiple Spray-Coated SWNTs on PES Substrates , 2009 .

[25]  C. Hagleitner,et al.  Smart single-chip gas sensor microsystem , 2001, Nature.

[26]  A. Freedman,et al.  Fluoropolymer-based capacitive carbon dioxide sensor , 2006 .

[27]  Ching-Liang Dai,et al.  A capacitive humidity sensor integrated with micro heater and ring oscillator circuit fabricated by CMOS–MEMS technique , 2007 .

[28]  Antonella Macagnano,et al.  Electronic nose and SPME techniques to monitor phenanthrene biodegradation in soil , 2008 .

[29]  D. Massart.  Chemometrics: A Textbook , 1988 .

[30]  Trond Ytterdal,et al.  A short-channel DC SPICE model for polysilicon thin-film transistors including temperature effects , 1999 .

[31]  Claude Pellet,et al.  Comparison of three humidity sensors for a pulmonary function diagnosis microsystem , 2002 .

[32]  Kuei-Ann Wen,et al.  A flexible mixed-signal/RF CMOS technology for implantable electronics applications , 2010 .

[33]  SeongHwan Cho,et al.  A 95nW ring oscillator-based temperature sensor for RFID tags in 0.13µm CMOS , 2009, 2009 IEEE International Symposium on Circuits and Systems.

[34]  Sigurd Wagner,et al.  Electrical response of amorphous silicon thin-film transistors under mechanical strain , 2002 .

[35]  Rui Igreja,et al.  Dielectric response of interdigital chemocapacitors: The role of the sensitive layer thickness , 2006 .

[36]  Sigurd Wagner,et al.  Flexible display enabling technology , 2001, SPIE Defense + Commercial Sensing.

[37]  Jan M. Rabaey,et al.  Digital Integrated Circuits , 2003 .

[38]  T. Afentakis,et al.  Design and fabrication of high-performance polycrystalline silicon thin-film transistor circuits on flexible steel foils , 2006, IEEE Transactions on Electron Devices.

[39]  Adisorn Tuantranont,et al.  Portable electronic nose based on carbon nanotube-SnO2 gas sensors and its application for detection of methanol contamination in whiskeys , 2010 .

[40]  David T. W. Lin,et al.  A Flexible Proximity Sensor Fully Fabricated by Inkjet Printing , 2010, Sensors.

[41]  Yoshihiko Sadaoka,et al.  Humidity sensors based on polymer thin films , 1996 .

[42]  Todd E. Mlsna,et al.  Chemicapacitive microsensors for volatile organic compound detection , 2003 .