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

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.