Spider-silk-inspired dynamic hard-soft ionogels enabled by solvation-contrast-guided phase separation.

Stretchable ionogels are promising epidermal biointerfaces, yet integrating mechanical robustness with efficient viscoelastic dissipation remains challenging. Inspired by the hard-soft hierarchical architecture of spider silk, we develop a phase-separated ionogel by copolymerizing N,N-dimethylacrylamide (DMAA) and acryloxyethyl trimethylammonium chloride (DAC) in an ionic-liquid matrix. Differences in polymer/ionic-liquid affinity and local ionic association are proposed to promote nanoscale heterogeneity, as supported by AFM, USAXS, spectroscopy, and molecular simulations. The resulting dynamically reconfigurable ionic associations enable effective load bearing and energy dissipation. The optimized PDCI-25 ionogel combines high strength, toughness, rapid stress relaxation, broadband damping, strong adhesion, and crack resistance. When integrated with conductive fabric, PDCI-25 functions as a hybrid epidermal electrode with lower low-frequency skin-electrode impedance and reduced motion artifacts compared with commercial Ag/AgCl electrodes. It consequently enables stable electromyography and electrocardiography recording under dynamic conditions, demonstrating its potential as a mechanically adaptive and motion-tolerant epidermal biointerface.