Sandcastle-Worm-Inspired Hydrogel Electronics for In Situ Forming, Reconfigurable, and Sustainable Bioelectronic Interface.

Hydrogel electronic biointerfaces represent a promising avenue for human-machine interaction. Establishing hydrogel interfaces that facilitate electronic coupling and biomechanical compatibility with biological surfaces is essential for reliable electrical recording and stimulation. However, this endeavor poses challenges due to the interfacial water on wet biological surfaces, compromising the intimate contact and stable functioning of bioelectronic interfaces. Inspired by sandcastle worms, which secrete inversely charged proteins to immobilize sand grains for stable anchoring, we propose water-absorbing and in situ forming hydrogel electronics, enabled by water-triggered self-crosslinking micro-xerogels. Upon contact with water, the micro-xerogels will undergo rapid physical self-crosslinking, resulting in the formation of bulk hydrogels. By eliminating interfacial water, sandcastle-worm-inspired hydrogel electronics (SHEs) could establish rapid (adhesion formation within 8 s), robust (adhesion energy >350 J·m-2), electrically conductive (>2.5 S·m-1), and conformal interfaces on biological surfaces. Besides, the SHEs exhibit practical reconfigurability, allowing reattachment to biological surfaces through rehydration after triggerable detachment and ethanol drying, while retaining bioelectronic functionalities comparable to the initial application. We further demonstrate the sustainability of SHEs with a recyclable process of freeze-drying, mechanical grinding into micro-xerogels, and reuse in reconfigurable interfaces. These studies provide a promising strategy for fabricating bio-inspired electronics with enhanced bioelectronic performance and improved reconfigurability.