Deep Eutectic Solvent Based Multifunctional Hydrogels for Strain Sensing and Electrophysiological Signal Monitoring.

Hydrogels are promising for flexible electronics due to their unique properties, but their practical use is hindered by freezing and dehydration in extreme environments. Inspired by natural cryoprotection, we designed a hydrophilic deep eutectic solvent (DES) composed of acryloyloxyethyltrimethylammonium chloride (AETC) and urea. This DES/H2O binary solvent was then polymerized into a multifunctional hydrogel via a facile one-step photopolymerization. The dense hydrogen-bonding network within the DES effectively confines the motion of water molecules, thereby endowing the hydrogel with exceptional anti-freezing properties (down to -80°C) and long-term moisture retention. The unique structural design, which features highly entangled polyelectrolyte chains and a dense network of dynamic sacrificial bonds that undergo breaking and reconstruction, enables the fabrication of an elastic hydrogel. Moreover, the as-prepared PAETC-urea hydrogels exhibit high transparency (95%), remarkable stretchability (>3000% elongation), strong adhesion to various engineering substrates, and efficient self-healing capability. These collective features ensure the reliable performance as a wearable strain sensor for accurately detecting human motions and high-fidelity electrophysiological signals, demonstrating great potential for next-generation flexible electronics.