Light‐Encoding of a Supramolecular Hydrogel for Assembly‐Free Soft Machines Capable of Sequential and Multistage Shape‐Morphing

Abstract Shape‐morphing hydrogels can mimic the dynamism of living creatures and are popular for designing soft machines, such as actuators and robots. However, most existing shape‐morphing hydrogels present a single morphing pathway between two shapes, sequential and multistage shape‐morphing in real scenarios has rarely been captured. Although a strategy that assembles functional hydrogel components has been reported, it is likely to simultaneously increase the complexity and weaken the versatility of hydrogel machines. Here, a light‐encoding strategy based on the dynamic coordination between the ferric iron and carboxyl group (Fe 3+ ─COO − ) to integrate the frame and actuating units into a single hydrogel without assembly is proposed. The spatiotemporal control of light irradiation is expected to make the light‐encoding process sequential and reprogrammable. Results demonstrate that the light‐encoded patterns determine the morphing route and further activate shape‐morphing owing to swelling mismatch. The actuating units can be successively created by localized irradiation or elaborately turned by re‐coordinating and light‐encoding. This endows the encoded hydrogel with sequential and multistage shape‐morphing behavior, similar to the living creatures. This strategy allows the design of assembly‐free soft machines with sequential and multistage shape‐morphing performance, which will benefit the design of more types of hydrogel machines.