Fig. 4. Schematic illustrates the applicability of the hydrogel actuator under different circumstances.

a jumping over a barrier, b rolling over an incline, c going across a slit, and d moving through a pellucid z-shaped pipe. The corresponding images of a–d are shown in e–g, h–j, k–m, and n–s, respectively. The images of e–g, h–j, k–m, and n–s are obtained from the Supplementary Movies 15–18, respectively.