Sweat-Enhanced Self-Adhesive Double-Network Hydrogel for Dynamic Skin Electrophysiology

Abstract

Electrophysiological monitoring is essential in healthcare and life sciences, yet conventional Ag/AgCl electrodes face challenges such as interfacial instability and motion artifacts. Herein, we propose a sweat-enhanced electrode design with a double-network hydrogel, comprising Ca²⁺-modified silk fibroin (SF) and poly(acrylic acid) grafted with N-hydroxysuccinimide ester (PAA-NHS). The obtained biocomposite, SF-PAA-NHS (BioSP), exhibits strong skin adhesion through covalent cross-linking and intermolecular forces, achieving an interfacial toughness of 411 J m^–2. Upon sweating, SF enhances adhesion by strengthening molecular mobility and mechanical interlocking, resulting in a nearly 23% increase in interfacial toughness. Additionally, sweat electrolytes boost BioSP’s ionic conductivity by about 45%, enhancing its electrophysiological monitoring capabilities. BioSP can also be combined with elastomers for excellent antidrying performance. Finally, high-fidelity and long-duration electrophysiological measurements validate the superior performance of the sweat-enhanced electrode, representing a significant advancement in skin electrode technology for reliable and durable monitoring on dynamic and sweaty tissue.