Hydrophobic Eutectogels for High-Humidity Environment Sensing

Gels with excellent ionic conductivity and high-humidity resistance are highly desired in practical applications due to their potential to create wearable soft electronics that maintain reliable performance under humid conditions. Herein, we designed a fully hydrophobic eutectogel by one-step copolymerization of glycidyl methacrylate and 2-phenoxyethyl acrylate within a hydrophobic deep eutectic solvent (DES) composed of 1-allyl-3-methylimidazolium chloride and methyl 4-hydroxybenzoate. The optimized eutectogel exhibited exceptional moisture tolerance, featuring a water contact angle > 107° and humidity-insensitive ionic conductivity (0.10 mS·cm −1 at 90% RH). Subsequently, we fabricated a strain sensor that demonstrated stable resistance responses to multi-scale human motions, such as finger, wrist, and elbow joint bending, under both ambient and high-humidity conditions. This stability arose from the covalently crosslinked hydrophobic polymer network and non-hygroscopic DES, effectively mitigating water-induced sensing instability. The hydrophobic eutectogel sensor establishes a transformative platform for next-generation wearables in personalized healthcare and extreme-condition sensing.