Novel film manufacturing technique lets robots walk on water

Imagine tiny robots zipping across the surface of a lake to check water quality or searching for people in flooded areas. This technology is moving closer to reality thanks to work by researchers at the University of Virginia’s School of Engineering and Applied Science. Inspired by nature and insects such as water striders that walk on water, they created two prototype devices that can propel themselves across liquid surfaces.

The first, called HydroFlexor, paddles across a surface using fin-like motions. The second, named HydroBuckler, “walks” forward with a buckling motion that mimics the water-walking insects. The key innovation that made this possible is a technology developed by the team called HydroSpread.

To float and move on the surface of a liquid, robots need ultrathin, flexible films. Traditional approaches to making such films involve manufacturing them on a rigid surface, such as glass, and then transferring them to water, which often damages or breaks the film. However, the HydroSpread technique allows the films to be made directly on the liquid.

Printing films on water

The researchers detail this process in a new paper published in the journal Science Advances. First, they deposited a liquid polymer ink onto the water’s surface, where it spread out to form an ultrathin, seamless film. Then a laser was used to cut and pattern the film, creating the legs and body shapes of the robot directly on the water. The films are bilayered, composed of two different layers. When heat from an external infrared source was applied, the two layers expanded at different rates. This difference caused the film to bend and buckle, creating movement.

“This work eliminates fragile postfabrication transfers in soft device manufacturing, bridging the gap between soft films and structure fabrication, and establishes a streamlined pathway for designing and deploying functional soft devices directly in liquid environments,” commented the research team in their paper.

The HydroSpread method is a major achievement in soft robotics. It works with various types of inks and liquids, making the scalable mass production of these complex devices possible. Ultimately, this technology enables scientists to transform flimsy film materials into robust soft devices that are ready for use in aquatic settings, such as monitoring water quality, aiding search and rescue efforts, or conducting environmental sensing.

Beyond robotics, the innovative technique could be used to create ultrathin, resilient films for wearable medical devices and highly durable, bendable components for next-generation electronics.

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