Overview

• Researchers reported the HydroSpread method in Science Advances, establishing a way to fabricate ultrathin soft-film devices directly on liquid surfaces.
• Liquid polymer ink spreads into a seamless film on water and an in-situ laser patterns the film into device geometries without any post-transfer step.
• Two proof-of-concept robots were demonstrated: HydroFlexor, which propels itself by paddling, and HydroBuckler, which advances using a buckling gait inspired by water striders.
• Actuation comes from bilayer films that bend or buckle under an overhead infrared heater due to differential thermal expansion, enabling controllable speed and turning by cycling heat.
• The team reports compatibility with multiple inks and liquids suggesting a path to scalable production, with potential applications in environmental sensing and water sampling, though the devices remain lab-scale prototypes.