Thermally Stable All-Natural Agar Eutectogels for Transient Iontronics

Iontronics has propelled the development of innovative devices that can be made transient and possess distinct functionalities as compared to traditional electronics. The combination of deep eutectic solvents (DESs), and eutectic solvents more broadly, and biopolymers has enabled the preparation of eutectogels, a group of ionically conducting materials capable of operating over a wider window of temperatures than hydrogels. However, eutectogels based on biopolymers generally exhibit limited thermal stability at high temperatures, which has limited their applicability in iontronics. In this study, the development of thermally stable eutectogels (melting point above 79 °C and degradation at ∼110 °C) is demonstrated by combining agar with hydrated eutectic solvents and sorbitol. Additionally, the all-natural agar-based eutectogel demonstrated high ionic conductivity (1.1–3.4 mS cm–1), tensile strength (140 kPa), and compression strength (500–600 kPa). Furthermore, the presence of choline chloride in the eutectic solvents imparts the eutectogels with notable antifungal activity against C. albicans, A. niger, and Corynespora sp. Leveraging these properties, the eutectogels were tested as transient strain sensors, broadening their application to next-generation wearable and soft robotics devices capable of resisting microbial colonization.