Gummy‐inspired natural eutectogels with high adhesiveness, toughness and humidity response

Abstract Biogel‐based ionic devices have emerged as versatile platforms for broad applications in wearable electronics, healthcare monitoring and bioelectronic interfaces. Electronic functions derived from fully edible natural soft materials are particularly attractive to allow low cost, green, biocompatible and biodegradable devices in biomedical areas as well as smart food package. This work presents a gummy‐inspired protein eutectogel by simply soaking gelatin hydrogels into solutions of natural deep eutectic solvent (NADES) consisting of sorbitol and citric acid to allow solvent exchange. Compared with the gelatin hydrogel, this natural eutectogel (NEG) exhibited anti‐drying and anti‐freezing performance, remarkably improved adhesiveness, room temperature degradability, as well as high mechanical toughness. The soaking conditions were investigated to tune the softness and ionic conductivity of the NEG, which revealed that the water content and acid ratio could significantly impact on the gel properties. Additionally, the eutectogel thin film exhibited good humidity sensing capability with a wide linear detection range (22%–98% RH), in which a soft patch was further demonstrated for breath test to detect various respiration frequencies. Thus, we believe the concept of NEG combining biopolymers and NADES can be explored in a broad range of soft devices for sensing, bio‐adhesives, energy supply or drug delivery.