Self-Adhesive Gelatin/Slide-Ring Double-Network Hydrogel for Human Motion Sensing and Morse Code Communication

Hydrogels emerge as highly promising candidates for wearable electronics due to their moldability and biocompatibility. However, hydrogel-based wearable electronics often suffer from poor mechanical properties and limited adhesion, pose significant challenges to their practical application. Herein, a conductive, stretchable, and self-adhesive gelatin/slide ring hydrogel (SRH) with a double-network (DN) structure is developed by incorporating a polyrotaxane (PR) based cross-linker in the hydrogel with the gelatin (GEL) network. The water-soluble allylic PR (APR) cross-linkers are prepared from the cyclodextrin-based PR via a simple one-step method. Additionally, the effect of APR cross-linkers with different sliding capabilities on the mechanical properties of SRH is further investigated aiming to optimize performance. The optimized SRH achieves a balance between toughness (2226 kJ m^-3) and rigidity (154 kPa), along with high stretchability (3048%) and strong adhesion to various substrate materials. More importantly, this DN hydrogel is demonstrated as a human motion sensor capable of Morse code communication. This work not only advances the understanding of slidable PR cross-linker applications but also paves the way for innovative hydrogels tailored for high-performance wearable electronics, broadening their scope and functionality in real-world use.