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

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 cm2 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.