Self-Healing and Freeze-Resistant Boat-Fruited Sterculia Seed Polysaccharide/Silk Fiber Hydrogel for Wearable Strain Sensors

This study introduces a sustainable bio-based hydrogel crafted from boat-fruited Sterculia seed polysaccharide (BF), silk fiber (SF), calcium chloride (CaCl2), and borax. The inherent hydrophilic groups and natural network structure of BF are conducive to the formation of a hydrogel with a high water content and a porous structure. The SF serves a dual role, providing structural support and acting as an antifreezing agent. The unique structure of this hydrogel is characterized by reversible dynamic cross-links, including hydrogen, borate ester, and Ca2+/–COOH coordination bonds, which endow it with excellent self-healing, mechanical, thermoreversible, and freeze-resistant properties. The bio-based hydrogel successfully adheres to various surfaces, including skin, and provides stable, repeatable electrical signals for the monitoring of diverse human movements (e.g., elbow and wrist movement) and subtle facial expressions. Moreover, the hydrogel exhibits excellent stability and reusability. Our study thus provides a convenient and environmentally friendly strategy for fabricating self-healing hydrogels with promising applications in healthcare monitoring or human–computer interactions.