Hydrophobic, ionically conductive, self-adhesive and fully recyclable eutectogels for stretchable wearable sensors and triboelectric nanogenerators†

Abstract

Eutectogels synthesized from deep eutectic solvents (DESs) have emerged as promising materials for flexible electronics due to their environmentally benign fabrication and multifunctional attributes. However, their practical use is hindered by inherent limitations such as pronounced hydrophilicity, suboptimal environmental adaptability, dependence on chemical initiators, and limited recyclability. Here, we report a novel strategy for fabricating hydrophobic eutectogels by exploiting the spontaneous ring-opening polymerization of thioctic acid within a polymerizable hydrophobic DES matrix to construct a dynamic polymer network. Further enhancement is achieved by integrating polymerizable ionic liquid monomers and microcrystalline cellulose via a synergistic combination of chemical and physical crosslinking, resulting in a robust hybrid network. The resultant eutectogels exhibit outstanding mechanical flexibility, underwater self-adhesion, and full-component recyclability. Notably, the dynamic ionic conductive network imparts highly sensitive and stable electrical responses when the eutectogel is employed as a strain sensor, exhibiting a gauge factor of 1.04 at deformations below 600% and a significantly enhanced gauge factor of 2.63 at higher deformations, while capable of detecting strains as low as 0.1%. This exceptional sensitivity and performance remain consistent even after 1200 cyclic tests. Moreover, a eutectogel-based triboelectric nanogenerator delivers an output voltage of up to 120 V, efficiently harvesting mechanical energy to power an array of 120 LEDs. These findings underscore the potential of the developed eutectogels as high-performance materials for wearable electronics, smart sensing, and sustainable energy conversion, paving the way for next-generation flexible electronic systems.