Dual‐Mode, Self‐Powered, and Flexible Humidity Sensor Based on Double‐Network Hydrogel with Multifunctional Applications

Abstract High‐performance and multifunctional humidity sensing have received wide attention in recent years. However, the problem is that sensors with a single signal output and requiring an external power source restrict their further application. Herein, a high‐performance dual‐mode, self‐powered, and flexible humidity sensor is proposed based on a double‐network functional ionic hydrogel via a hydrogen bond‐rich strategy, resulting in stable humidity sensing performance under different bending states. A 0.56 cm 2 of hydrogel‐based sensor achieves 16000 times of resistance change at 95% RH (relative humidity) and generates an output voltage of 0.62 V at 43% RH with good linearity and small hysteresis. Further, the sensor shows outstanding voltage output stability with ≈95% performance retention after 1000 times of bending, and with an output power density of 1.14 µW cm −2 . As a proof of concept, the potential applications of the miniaturized device in respiratory monitoring, emotional analysis, finger discrimination, and portable energy harvesting are evaluated.