Bioinspired light-fueled water-walking soft robots based on liquid crystal network actuators with polymerizable miniaturized gold nanorods

Walking on water is a unique locomotion mode found in aquatic living creatures. However, it remains challenging to create light-driven aquatic soft robots that can walk freely on water surface. Herein, water strider-inspired water-walking soft robots that can be remotely controlled by light are demonstrated through combining superhydrophobic floating surface with hierarchical nanostructures and light-driven soft-actuation legs that are fabricated through in situ embedding of judiciously designed polymerizable miniaturized gold nanorods (MiniGNR nanomonomer) in liquid crystal network (LCN)-based soft actuators. The MiniGNRs-LCN soft actuators act as driving paddles to enable propulsive motion on the water surface, and the superhydrophobic surface facilitates the aquatic soft robots with weight-bearing and drag-reducing ability. Upon cyclic exposure to near-infrared light, the LCN-based actuation leg quickly exhibits a photoinduced shape-bending deformation, enabling the one-legged soft robot to walk on water surface unidirectionally through horizontal momentum transfer of photoinduced actuation force to the water. Taking advantage of tailorable photoresponsiveness of MiniGNR nanomonomer, a tri-legged water-walking soft robot that can execute visible/infrared wavelength-dependent multi-directional motions is further demonstrated for cargo transportation. This research may provide a new toolbox for the development of untethered soft robots with sophisticated spatiotemporal actuation toward aquatic complex environments.