Protonation-Mediated Multifunctional Silk Fibroin Hydrogel Adhesives for Epidermal Interface Sensing
Silk fibroin (SF)-based hydrogels are promising for biological interfaces, yet achieving multifunctionality—mechanical robustness, adhesion, conductivity, and stability—often requires chemical modification that compromises biocompatibility. Here, we report a protonation-mediated SF/polyvinyl alcohol (PVA) hydrogel adhesive that retains natural silk properties while gaining tailored functionalities. The physically crosslinked network is formed solely via molecular interactions, with phosphoric acid (H3PO4) as a protonation agent to modulate hydrogen bonding, enabling precise control over adhesion, mechanical strength, and electronic conductivity. Glycerol (Gly) is incorporated as a moisturizing agent to enhance long-term stability for skin applications. The resulting hydrogel exhibits excellent performance in monitoring electrophysiological signals, including electrocardiogram (ECG), electromyogram (EMG), and electroencephalogram (EEG), demonstrating its potential as a platform for advanced biological interfaces. This work addresses the critical challenge of developing SF-based hydrogels that combine natural advantages with multifunctionality, offering a promising route for wearable health monitors and human-machine interfaces.