A wireless low-range pressure sensor based on P(VDF-TrFE) piezoelectric resonance

Abstract

A low-range bio-compatible pressure sensor based on P(VDF-TrFE) piezoelectric resonance has been tested and integrated to a wireless platform. Many critical physiological applications and in vivo diagnosis require highly sensitive pressure monitoring in the 0–100 kPa range, with negligible long-term drift and robust integration platform. The PVDF film and its copolymers exhibit significant piezoelectric properties after poling. P(VDF-TrFE) is preferred for its flexible film structure, low modulus, high yield strength and resistance to corrosive chemicals. All piezoelectric materials are lossy and thus the leakage current will cause drift of instantaneous response, which limits the direct use of piezoelectric charges in sensing. In this paper, the pressure sensor which adopts the appropriate properties of P(VDF-TrFE) for low pressure levels, works as an acoustic wave resonator to avoid long-term drift from the charge leakage problem in quasi-static pressure, while maintaining good sensitivity. Simulation results show good agreement with the measurement data. The temperature coefficient and the areal scaling effect are characterized. Furthermore, the sensor output is matched with standard 50 Ω impedance at the resonance for integration into the RF circuits. A passive sensor tag is demonstrated by using RF backscattering.