Environment-tolerant versatile ion-conductive eutectic hydrogels for self-powered wearable flexible sensors

Conductive hydrogels (CHs) have been widely utilized in the design of wearable flexible sensors. The remaining issues with CHs include their propensity to dehydrate in the open air and freeze at low temperatures, which makes them significantly less functional. Additionally, the wide applications of CHs are limited by their dependence on external power sources and inadequate sensing of humidity, strain, etc. Herein, a series of versatile ion-conductive adhesive hydrogels (GAAAD) with emblematic on-demand 3D cross-network structures were nanoengineered by combining solvent exchange strategies with in-situ physical and covalent cross-linking. The GAAAD possesses exceptional properties such as integrated outstanding sensing of multiple external stimuli in harsh environments, desirable adhesive ability towards various substrates, mechanical robustness, transparency, anti-freezing and anti-dehydration performance, and self-healing capacity. Even after being frozen at −20 ℃ for 48 h, GAAAD could be utilized for effective real-time human sleeping monitoring, demonstrating preponderant environmental stability. Integrated with the versatile origins of GAAAD, a simple Cu/GAAAD/Zn self-powered flexible sensor (GAAADB) was developed based on the fundamental structure of a primary battery, which exhibits remarkable properties of stable open-circuit voltage even in extremely cold environments, sensitive response to applied tensile or compressive strain, as well as its repeatability and durability. Interestingly, based on the sensing mechanism of the potential difference between the humidity-regulating electrodes, GAAADB was substantiated to be reliable for long-term respiratory monitoring (with the humidity response/recovery time less than 1 s) under extreme cold conditions (−20 °C), indicating its great potential for extensive applications in respiratory diagnosis, sleep monitoring, electronic skin, and wearable electronics.