Jumping on water: Surface tension–dominated jumping of water striders and robotic insects

TLDR

Jumping on water is a unique locomotion mode found in semi‑aquatic arthropods such as water striders. The study aims to reproduce this feat in a surface‑tension‑dominated robot by elucidating hydrodynamics and applying them to design a bio‑inspired impulsive mechanism that maximizes momentum transfer to water. The authors built a 68‑mg at‑scale robotic insect that uses this impulsive mechanism to achieve maximum momentum transfer and successfully jump on water. The results reveal that water striders rotate their leg tips inward at low descending velocity with forces just below the water‑surface‑break threshold, and that the robot’s design reproduces these hydrodynamic principles, demonstrating effective water‑jumping and offering a method to replicate such capabilities in artificial systems.

Abstract

Jumping on water is a unique locomotion mode found in semi-aquatic arthropods, such as water striders. To reproduce this feat in a surface tension-dominant jumping robot, we elucidated the hydrodynamics involved and applied them to develop a bio-inspired impulsive mechanism that maximizes momentum transfer to water. We found that water striders rotate the curved tips of their legs inward at a relatively low descending velocity with a force just below that required to break the water surface (144 millinewtons/meter). We built a 68-milligram at-scale jumping robotic insect and verified that it jumps on water with maximum momentum transfer. The results suggest an understanding of the hydrodynamic phenomena used by semi-aquatic arthropods during water jumping and prescribe a method for reproducing these capabilities in artificial systems.