The concept of walking on water might sound supernatural, but in fact it is a quite natural phenomenon. Many small living creatures leverage¹ water's surface tension to maneuver² themselves around. One of the most complex maneuvers³, jumping on water, is achieved by a species of semi-aquatic insects called water striders that not only skim along water's surface but also generate enough upward thrust with their legs to launch themselves airborne from it. Now, emulating⁴ this natural form of water-based locomotion⁵, an international team of scientists from Seoul National University, Korea (SNU), Harvard's Wyss Institute for Biologically Inspired Engineering, and the Harvard John A. Paulson School of Engineering and Applied⁶ Sciences, has unveiled a novel robotic insect that can jump off of water's surface. In doing so, they have revealed new insights into the natural mechanics that allow water striders to jump from rigid⁷ ground or fluid water with the same amount of power and height. The work is reported in the July 31 issue of Science.

 

"Water's surface needs to be pressed at the right speed for an adequate amount of time, up to a certain depth, in order to achieve jumping," said the study's co-senior author Kyu Jin Cho, Associate Professor in the Department of Mechanical and Aerospace⁸ Engineering and Director of the Biorobotics Laboratory at Seoul National University. "The water strider is capable of doing all these things flawlessly."

 

The water strider, whose legs have slightly curved tips, employs a rotational⁹ leg movement to aid it its takeoff from the water's surface, discovered co-senior author Ho-Young Kim who is Professor in SNU's Department of Mechanical and Aerospace Engineering and Director of SNU's Micro Fluid Mechanics Lab. Kim, a former Wyss Institute Visiting Scholar, worked with the study's co-first author Eunjin Yang, a graduate researcher at SNU's Micro Fluid Mechanics lab, to collect water striders and take extensive videos of their movements to analyze¹⁰ the mechanics that enable the insects to skim on and jump off water's surface.

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