A Bistate Intelligent Eutectogel Material with Water‐Regulated Stiffness for Diverse Designed Functionality

The design of stiffness‐changeable synthetic materials that can mimic their biological counterparts in the production of adaptable structures and functions is highly important but remains challenging. Here, the development of a bioinspired intelligent material composed of a deep eutectic solvent (DES) and an ionically crosslinked polymer network that is capable of switching reversibly between hard plastic and soft elastic states in response to water is reported. The eutectogel stiffness can be dramatically switched and flexibly regulated by water, which can activate salt ionization and shield the ionic crosslink. This design principle is extensively applied to multiple polymers, producing a series of bistate materials that exhibit water‐regulated capabilities ranging from self‐healing, shape memory, remolding, antifreezing, anticompressing, and stretchability to conductivity. These bistate materials are used for diverse functions, such as performing mechanical tasks, sensing and monitoring human movements, lighting LEDs, and outputting signals. This work opens an avenue for the development of next‐generation stiffness‐changeable materials with diverse functionalities for various designed applications.