Rapid Thermoresponsive Double-Network Hydrogel with Dynamic Cross-Linking for Self-Powered Wearable Sensors and Fire Detection Systems

Hydrogel materials show significant promise for wearable devices and environmental sensing applications, yet conventional hydrogels suffer from poor mechanical durability and sluggish responsiveness to stimuli. To overcome these limitations, we developed a dual-network hydrogel (PAMSa) by integrating polyacrylamide (PAM) and sodium alginate (SA) networks with Cu 2+ ions as dynamic cross-linking agents, successfully achieving simultaneous temperature sensitivity, self-powering capability, and robust mechanical performance in the PAMSaC-2 formulation. Characterization revealed that the hydrogel exhibits mechanical properties (650% strain, 247 kPa stress) alongside competitive electrical conductivity (0.264 S/m at 20 °C), with elevated temperatures inducing a phase transition of bound Cu 2+ ions to mobile states that slightly reduces mechanical strength but significantly enhances conductivity (0.361 S/m at 70 °C) and improves energy supply efficiency in self-powered systems. A stacked series configuration of PAMSaC-2 synchronously amplifies voltage and current to directly power miniature devices like fans and oximeters, while its resistance changes enable real-time human joint motion monitoring with high sensitivity. Notably, a PAMSaC-2-based fire-warning system maintains reliable detection accuracy even after prolonged storage. This study establishes a paradigm for multifunctional integration in smart hydrogels, bridging mechanical resilience, adaptive functionality, and energy autonomy for next-generation wearable electronics and environmentally responsive sensors.