Researchers at the University of Virginia’s School of Engineering and Applied Science have developed a fabrication method for soft robots that can operate directly on water surfaces. The work, led by Baoxing Xu, professor of mechanical and aerospace engineering, is detailed in a study published in Science Advances.
The method, called HydroSpread, enables the creation of ultrathin, flexible films directly on liquid surfaces. Traditionally, such films were produced on rigid substrates and then transferred to water, a process prone to damage. By allowing droplets of liquid polymer to spread into uniform sheets on water and using a laser to cut them into precise shapes, the UVA team has introduced a way to construct soft robotic devices without the transfer step.
Using this approach, the researchers designed two prototypes. HydroFlexor moves by paddling with fin-like motions, while HydroBuckler advances by buckling its leg-like structures, inspired by water striders. In experiments, both devices were powered by infrared heating, which caused their layered films to bend or buckle. By adjusting the heat cycles, the researchers demonstrated controllable motion, including changes in speed and direction.
Xu noted that building directly on liquid reduces failure in the fabrication process and improves precision. Beyond soft robotics, the method could be applied to the development of wearable medical sensors, flexible electronics and environmental monitoring systems, where thin, adaptable materials are required.
Photo credit: Baoxing Xu, UVA School of Engineering and Applied Science
