Capacitive pressure sensor with high sensitivity and wide pressure detection range based on a micro-porous elastomer dielectric layer fabricated via supercritical carbon dioxide foaming

Porous elastomer dielectric layer has attracted more and more attentions in capacitive pressure sensor (CPS) because of its strong deformability and large compressive strain. In this work, a simple, low cost and eco-friendly method of supercritical carbon dioxide foaming is first utilized to fabricated micro-porous elastomer dielectric layer for the CPS. By adjusting foaming temperature, a uniform micro-porous structure with thinner pore wall and larger pore size is obtained. Such micro-porous structure of the elastomer dielectric layer enables the corresponding CPS with significantly higher sensitivity than the CPS with the solid dielectric layer. The sensitivity of the former can be as high as about 53 times higher than that of the latter. By characterizing and analyzing the mechanical and dielectric properties of the elastomer dielectric layer, the mechanism for improvement on pressure sensing performance by the micro-porous structure is revealed. Via adjusting the saturation pressure and thus optimizing the porous structure, the sensing performance of the CPS is further improved. And the CPS with higher sensitivity and wider pressure detection range was obtained. The fabricated micro-porous TPU-based CPS exhibits good cyclic stability and durability, and can well detect the dynamic and static pressure for the human motion detection.