Ionic Liquid-Mediated Phase Separated Hydrogels With Bicontinous Conductive Networks for Long-Term Underwater Strain Sensing

Ionic conductive hydrogels have attracted significant attention as wearable sensors due to their intrinsic flexibility, biocompatibility, and excellent sensing properties. Nevertheless, their practical applications in underwater environments are limited by challenges such as hydrogel swelling and ionic components leaching. Herein, a hydrophobic ionic liquid (IL)-mediated molecular engineering strategy is presented to fabricate underwater-stable conductive hydrogels integrated with anti-swelling and adhesion properties. The strategy utilizes a DMSO-IL binary solvent that exploits differential polymer-water affinity to drive phase separation. Notably, hydrophobic IL enhances phase separation through multiple interactions with hydrophilic groups while constructing a bicontinuous conductive network within the hydrogel. The strategic incorporation of poly(vinyl alcohol) (PVA) increases the cross-linking density, enhancing the mechanical and anti-swelling performance of the hydrogel. The fabricated hydrogels are utilized as wearable sensors featuring reliability and wide sensing ranges for underwater communication and human motion detection. The hydrogel sensor could withstand 400 stretching-releasing cycles and 1 month of immersion in water, with negligible performance change. This molecular design strategy advances the development of durable ionic conductive hydrogels for underwater electronics, addressing key limitations in underwater sensors.