Chemical Reaction‐Powered Self‐Assembly and Dehydration of Supramolecular Hydrogels for Phase‐Transitional Robots

ABSTRACT Phase‐transitional robots have long intrigued the scientists from multidisciplinary fields, yet their realization remains a formidable task due to the lack of soft materials that seamlessly integrate phase transition with actuation functionality. Here, we report phase‐transitional hydrogel robots enabled by chemical reaction‐powered supramolecular gelation of a peptide solution followed by a dehydration process. The peptide contains a carboxyl group which can be converted into hydrophobic oxazolone moiety upon addition of carbodiimide. This chemical transformation neutralizes the negative charge of the peptide, thereby activating its self‐assembly into a hydrogel. Interestingly, over time, the hydrogel network becomes more hydrophobic because of the progressive formation of hydrophobic oxazolone species, which in turn leads to dehydration‐induced macroscopic contraction of the hydrogel. The contraction degree can be regulated by changing the concentrations of carbodiimide. This sol‐to‐gel transition followed by actuation behavior enables phase‐transitional robots that can flow into complex terrains to catch and transport cargoes, showing extraordinary morphological adaptivity. As an application, we show that the robot can adaptively enter a narrow channel to regulate an electrical circuit. This work unlocks the potential of chemically fueled supramolecular self‐assembly for the development of phase‐transitional robots that show unparalleled morphological adaptivity and functionalities.