Soft Capacitive Pressure Sensors: Trends, Challenges, and Perspectives

TLDR

Soft capacitive pressure sensors are essential for e‑skins in soft robotics and bioelectronics, offering high flexibility, sensitivity, and stability, yet their practical use is limited by sensitivity loss at higher pressures and coupling between stretch and pressure responses. This perspective investigates alternative strategies beyond porous or high‑dielectric soft dielectrics to address sensitivity decay and stretch–pressure coupling, and discusses broader considerations for widespread e‑skin deployment.

Abstract

Soft pressure sensors are critical components of e-skins, which are playing an increasingly significant role in two burgeoning fields: soft robotics and bioelectronics. Capacitive pressure sensors (CPS) are popular given their mechanical flexibility, high sensitivity, and signal stability. After two decades of rapid development, e-skins based on soft CPS are able to achieve human-skin-like softness and sensitivity. However, there remain two major roadblocks in the way for practical application of soft CPS: the decay of sensitivity with increased pressure and the coupled response between in-plane stretch and out-of-plane pressure. In addition to existing strategies of building porous and/or high dielectric constant soft dielectrics, are there any other promising methods to overcome those bottlenecks? Are there any further considerations for the widespread deployment of e-skins? This perspective aims to shed some light on those topics.