Multifunctional eutectogels with superionic conductivity comparable to advanced hydrogels

Conductive hydrogels are promising for flexible wearable sensors owing to their high conductivity, flexibility, and tunable mechanical attributes; however, their poor environmental stability limits their practical use. Eutectogels prepared using deep eutectic solvent (DES) offer improved stability, yet their conductivity typically falls short of advanced hydrogels (around 10^-1 S cm^-1 at room temperature). To address this, we developed a one-pot synthesized eutectogel (denoted as DHA) using a DES composed of sulfamic acid (SA) and ethylene glycol (EG) as the solvent, incorporating polyoxometalates (POMs, specifically H₃PW₁₂O₄₀) as conductive fillers within a polyacrylamide (PAM) network. In the DHA eutectogel, POMs endow the gel with both proton-conducting and photochromic properties, while SA plays multiple roles: it serves as a hydrogen-bond acceptor in the DES, a proton source, and a bridging unit that connects adjacent POMs to facilitate proton hopping and boost conductivity. The resulting DHA eutectogel achieves high proton conductivity (0.199 S cm^-1 at 25 °C), exceptional anti-freezing performance (down to -99.9 °C) and anti-drying properties (retaining over 103% weight after 40 days), alongside strong adhesion, high stretchability, and reversible photochromism. Furthermore, a multifunctional sensor derived from the DHA eutectogel exhibits high sensitivity for accurate, stable, and real-time human activity monitoring across a wide temperature range. This work utilizes the synergistic effect of DES and conductive filler to achieve eutectogels with high conductivity, offering an innovative route toward flexible sensing materials that combine high conductivity and outstanding environmental stability.