Hydrophobic deep eutectic solvent-based eutectogels for long-term humidity resistance and multifunctional sensing

Eutectogels based on deep eutectic solvents (DESs) hold significant potential for application in flexible sensors. However, their hygroscopic nature limits their use in humid environments. In this study, a eutectogel with excellent long-term humidity resistance was developed via radical copolymerization of acrylic acid monomers in a hydrophobic DES (HES). The hydrophobicity of the HES makes the gel highly stable under humid conditions, with a water absorption rate of only 2.8% at 30 °C and 90% relative humidity over 30 d. Even after storage in a humid environment for 365 d, the gel maintained its tensile mechanical properties (retaining 99.3% of toughness) and shape. In addition, the gel exhibits several outstanding properties. Sensors fabricated from these gels demonstrate high sensitivity to strain, pressure, and temperature, along with excellent durability in humid environments. These sensors are capable of real-time monitoring of various human activities and deliver stable signal output. This work paves the way for the development of long-lasting gels and lays a foundation for the advancement and application of functional gel materials.