Tiny robot inspired by water striders skims across water at high speed

Researchers have uncovered the mechanism behind the remarkable speed and agility of Rhagovelia water striders, tiny insects that skim rapidly across turbulent streams. Unlike previous assumptions that their fan-like leg propellers were muscle-powered, the study found these ribbon-shaped fans open and close passively, driven by surface tension and elastic forces. This passive morphing enables a biomechanical duality—high flexibility during leg recovery and high rigidity during propulsion—allowing the insects to execute sharp turns and reach speeds up to 120 body lengths per second, rivaling the rapid movements of flying flies. Inspired by these biological insights, a multidisciplinary team from the University of California, Berkeley, Georgia Institute of Technology, and Ajou University developed an insect-sized robot named Rhagobot. Using high-resolution electron microscopy, they revealed the microstructure of the natural fans and engineered a one-milligram, self-deploying elastocapillary fan with a flat-ribbon shape that mimics the natural design. Integrated into the mic