Flexible Pressure Sensors Based on Screen-Printed P(VDF-TrFE) and P(VDF-TrFE)/MWCNTs

Abstract

This paper presents large-area-printed flexible \npressure sensors developed with an all screen-printing technique. \nThe 4×4 sensing arrays are obtained by printing Polyvinylidene \nFluoride-Trifluoroethylene P(VDF-TrFE) and their \nnanocomposite with multi-walled carbon nanotubes (MWCNTs) \nand are sandwiched between printed metal electrodes in a parallel \nplate structure. The bottom electrodes and sensing materials are \nprinted sequentially on polyimide (PI) and polyethylene \nterephthalate (PET) substrates. The top electrodes with force \nconcentrator posts on backside are printed on a separate PET \nsubstrate and adhered with good alignment to the bottom \nelectrodes. The interconnects, linking the sensors in series, are \nprinted together with metal electrodes and they provide the \nexpandability of the cells. Different weight ratios of MWCNTs are \nmixed in P(VDF-TrFE) to optimize the percolation threshold for a \nbetter sensitivity. The nanocomposite of MWCNTs in piezoelectric \nP(VDF-TrFE) is also explored for application in stretchable \ninterconnects, where the higher conductivity at lower percolation \nratios are of significant importance compared to the \nnanocomposite of MWCNTs in an insulator material. To examine \nthe functionality and sensitivity of sensor module, the capacitancevoltage \nanalysis at different frequencies, and the piezoelectric and \npiezoresistive response of the sensor are presented. The whole \npackage of foldable pressure sensor is completely developed by \nscreen-printing and is targeted towards realization of low-cost \nelectronic skin.