Underwater adhesive hydrogels: Interfacial failure mechanisms, engineering strategies, and wearable electronics

Underwater adhesive hydrogels are promising materials for wearable electronics because they combine mechanical compliance, interfacial adhesion, and electrical responsiveness. However, interfacial water, weakened adhesive interactions, and immersion-induced swelling can destabilize both adhesion and signal output. Recent advances have improved underwater adhesion by coordinating interfacial water regulation, adhesive bonding, and hydrogel network stability. Nevertheless, a systematic framework linking failure mechanisms, materials design, and wearable electronic applications is still lacking. This review discusses hydration-layer interference, interfacial bonding failure, and swelling-induced cohesion loss, and relates these mechanisms to representative engineering strategies. Applications in motion monitoring, physiological sensing, and human–machine interfaces are also summarized, together with the remaining challenges and future directions.