Enhancing Sensitivity of Piezoresistive Pressure Sensor at Low Pressures Using Photo-Sensitive Resin Plate as Flexible Substrate

Abstract

In this paper, flexible highly sensitive piezoresistive pressure sensors for low compressive stress detection (9.8 Pa to 10.7 kPa) are proposed, by using Photo-Sensitive Resin Plate (PSRP). The photolithography method is employed to create the micro-dome structure pattern on PSRP. Finally, the active parts of the sensors are made by depositing a thin layer of silver (Ag), as the sensing element, on the micro-dome patterns. Herein, the effect of three different surface pattern dimensions as well as two different thicknesses of the Ag layer on sensor sensitivity are evaluated. The sensor fabricated with a diameter of 300 µm for micro-dome structure, and 70 nm for the thickness of Ag layer demonstrated ultrahigh sensitivity of 29343 and 5 × 10⁶ kPa⁻¹ in the pressure ranges of 0.2–5 and 5–10.7 kPa, respectively. The sensor with a diameter of 300 µm for micro-domes and an Ag-thickness layer of 100 nm has a low working voltage of 0.1 V, a high sensitivity of 223.69 kPa⁻¹ in the pressure range <0.11 kPa, and lowest limit of detection 9.8 Pa. The response and recovery times of this sensor are 270 and 60 ms, respectively. Furthermore, the sensor maintained high and stable performance over a 17-min period.