Programmable Multistable Hydrogel Morphs

Abstract

Self‐shaping materials have wide applications in soft robotics, biomedical devices, etc. Shape transformations of intelligent materials are usually realized by switching environmental conditions. However, it is challenging to form multistable morphing structures under the same condition. Herein, the programmed deformations of a composite hydrogel into multistable configurations under the same condition are demonstrated. The hydrogel consists of integrated units of through‐thickness and/or in‐plane gradient structures, where the former leads to bending, folding, or twisting with a predetermined direction and the latter buckles upward or downward with equal possibility. The bistability of buckling affords the integrated hydrogel with multiple possible configurations. The composite hydrogel with multiple in‐plane gradient units (number: n ) and through‐thickness gradient ones (number: m ) theoretically has 2 n × 1 m = 2 n configurations under the same condition. Although the integration of units with through‐thickness gradient does not contribute to the diversity of configurations, it favors forming complex and designable configurations. Both experimental and simulation results show that various stable configurations can be obtained in one composite hydrogel under the same condition by controlling the buckling direction of each unit by a selective preswelling step. This concept and strategy are applicable for other intelligent materials and merit their applications in diverse areas.