Stretchable and Thermally Responsive Semi‐Interpenetrating Nanocomposite Hydrogel for Wearable Strain Sensors and Thermal Switch

Abstract Wearable electronics based on stimuli‐responsive hydrogels are promising in various applications such as soft robots, artificial skin, and health monitoring. Herein, a novel wearable and strain/thermal dual sensor is developed utilizing a nanocomposite hydrogel, which is prepared by incorporating allyl mercaptan (ALM) functionalized Au nanoparticles (Au@ALM) into poly( N ‐isopropylacrylamide‐ co ‐hydroxyethylmethacrylate)/poly( N ‐isopropylacrylamide) (P(NIPAM‐ co ‐HEMA)/PNIPAM) semi‐interpenetrating hydrogel network. PNIPAM acts as the thermally responsive component. Semi‐interpenetrating network and Au nanoparticles are introduced to enhance the mechanical properties of the hydrogel. Au nanoparticles also work as the electrically conductive component. Strain sensor and thermoreceptor are realized by using the mechanical stretchability and strain‐ or temperature‐dependent conductivity. The strain sensor exhibited excellent stability and repeatability in the strain range of 0–150%. Remarkably, the thermal sensor made of this hydrogel can monitor the ambient temperature from 0 to 70 °C. Therefore, an intelligent thermal switch is designed that can effectively protect electronic components by disconnecting high‐temperature circuits. The nanocomposite hydrogel holds great potential in smart devices and flexible sensors.