“Salt washing” adjustment of crosslinking degree to fabricate multifunctional antifreeze hydrogel for self-power and storage integrated flexible sensor

Hydrogel-based electronic skins or triboelectric nanogenerator (TENG) are considered ideal candidates for flexible electronics. However, current hydrogels face limitations that lead to suboptimal performance, and their reliance on external power sources hampers their practical application. A two-step washing approach comprising of “salt soaking” and “salt washing” is introduced to fabricate the multifunctional hydrogel. Initially, the hydrogel framework (SAC2Z)-acrylamide (AM) and silk fibroin (SF) hydrogel is formed via salt soaking. Subsequently, the crosslinking degree is fine-tuned by adjusting the salt ion concentration through salt washing. The obtained hydrogel SAC2ZC possesses excellent mechanical properties (a 15-fold increase in fracture strength to 320 kPa) and excellent cold resistance up to −80 °C. Compared to conventional water-dispersible hydrogels, strain sensors based on SAC2ZC are capable of sensing up to −30 °C. The flexible antifreeze battery based on SAC2ZC has excellent dendrite resistance and could supply power under high pressure (30 MPa) and severe bending (180°). The SAC2ZC-based TENG (C-TENG) enables energy harvesting, eliminating reliance on external power sources. This innovation paves the way for flexible sensing systems that integrate energy collection and storage, facilitating all-weather human-smartphone signal interaction. This research provides a new strategy to develop multifunctional SAC2ZC hydrogel for flexible wearable devices, especially in extremely cold complex environments.