Controlling Self-Oscillation of a Single-Layer Liquid Crystal Elastomer at the Air-Water Interface via Light Programming for Water Strider-Inspired Aquatic Robots

Biomimicking aquatic organisms offers many opportunities for designing intelligent robots that can freely move on water. However, most works were focused on multilayered materials or assembled structures and faced limitations in stability, versatility, and motion navigation. Here, we develop an assembly-free water-strider-like aquatic robot using a single layer of light-programmable liquid-crystal elastomer (LCE) that could be used to create asymmetric structures. The LCE strider mimics both the shape and functions of natural water striders; it is designed with four legs, with the fore and hind legs being programmed respectively via light. Consequently, the LCE strider shows self-oscillation and self-propulsion behaviors on low-grade thermal water with a temperature gradient at the air-water interface, owing to unbalanced changes in the contact areas and tensions between the legs and water. Furthermore, the trajectories of the LCE strider are manipulated by NIR light after selectively depositing polydopamine with photothermal conversion. In this way, path navigation is realized, that is, moving straight and on-demand turning, similar to the movement of natural water striders. This study should inspire the development of soft intelligent robots using shape-morphing materials.