Hybrid foam pressure sensor utilising piezoresistive and capacitive sensing mechanisms

Abstract

Abstract The development of flexible and stretchable sensing for future applications, e.g. strain, force and pressure, requires novel foam and foam-like structures with properties such as fast relaxation times, a wide linear response range, good sensitivity to different stimuli and repeatability, without compromising low-cost, simple and effective manufacturing methods and excellent mechanical properties. We present a new type of hybrid foam pressure sensor that utilises a combination of piezoresistive and capacitive sensor elements. The hybrid foam sensor shows maximum pressure sensitivity of 0.338 kPa⁻¹ and linear response of 0.049 kPa⁻¹ in the piezoresistive and capacitive sensor elements, respectively, in pressure ranges of <5 kPa and 0–240 kPa, respectively. The response and recovery times of both sensor elements were similar, ≤ 200 ms, at various pressures. In addition, the properties of the hybrid foam sensors, e.g. sensitivity and response and recovery times, can be tuned in various ways, such as by changing the thickness of the composition of the foam. Also, the materials are easily accessible and the sensor can be cost-effectively manufactured and changed for different purposes. The relatively high sensitivity of the piezoresistive sensor element enables object manipulation from low pressure (≥ 21 Pa) to high pressure (> 80 kPa). Simultaneously, both sensor elements can be used for impact measurements across a wide range of pressures up to ≥ 240 kPa. Thus, the concept of the hybrid foam sensor could be utilised widely for sensing of pressures, impacts or even bending in various applications, e.g., wearable electronics