Highly Sensitive Conformal Pressure Sensing Coatings Based on Thermally Expandable Microspheres

Abstract Great progress has been made to enhance the sensitivity of flexible pressure sensors recently. However, the format of these sensors has largely been limited to thin films. A highly sensitive pressure sensor based on coatings, which can ensure uniform coverage over large area as well as conformal contact with complex surfaces because of the flowability before solidification, has rarely been reported. Here, a highly sensitive capacitive pressure sensing coating is demonstrated for the first time. This sensor utilizes conductive composite coatings as electrodes and thermally expandable microspheres/polydimethylsiloxane composite coating as the dielectric layer. The expanded microspheres greatly enhance the compressibility and thus increase the sensitivity of the pressure sensors to 0.201 kPa −1 under 50 kPa. At the same time, it achieves the largest pressure‐sensing range in capacitive pressure sensors so far from 10 Pa to 4.5 MPa with a sensitivity of 3 × 10 −4 kPa −1 . It also features low hysteresis and good stability against repeated compression. More importantly, the format of coating not only reduces the cost and complexity of fabrication, but also facilitates the applications on surfaces with complex shapes, which paves the way for facile and economic application of flexible pressure sensors in the future.