Fabrication technology of piezoresistive conductive PDMS for micro fingerprint sensors

This paper reports the characterization of piezoresistivity of Conductive Polydimethylsiloxane (CPDMS) and the corresponding fabricating process for a parylene-coated, CPDMS Micro Fingerprint Sensor (MFS) with mushroom-shaped electrodes. Gauge factor of about 7.4 was demonstrated, and the piezoresistive sensitivity was about 3x10^-6 Pa^-1 in the tensile test setup. The packaged MFS sensors were characterized by a pneumatic test and a nanoindentation test. We demonstrate that the fabricated device can detect pressure and force levels bellow 10 kPa and 50 muN, respectively. The use of the material and process presented in this paper offers the opportunity to realize a robust micro fingerprint sensor with low cost, low temperature process on different substrates.