Researchers have developed an insect-sized robot that mimics a water strider to jump on the surface of a body of water.
Researchers at Seoul National University (SNU) in Seoul, South Korea, Harvard's Wyss Institute for Biologically Inspired Engineering, and the Harvard John A Paulson School of Engineering and Applied Sciences, studied a species of semi-aquatic insects called water striders.
The water strider, whose legs have slightly curved tips, employs a rotational leg movement to aid its takeoff from the water's surface, discovered co-senior author Ho-Young Kim, 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 analyse the mechanics that enable the insects to skim on and jump off water's surface.
By studying water striders in comparison to iterative prototypes of their robotic insect, the team discovered that the best way to jump off of water is to maintain leg contact on the water for as long as possible during the jump motion.
Mimicking these mechanics, the robotic insect built by the team can exert up to 16 times its own body weight on the water's surface without breaking through, and can do so without complicated controls.
The robotic insect was built using a "torque reversal catapult mechanism" inspired by the way a flea jumps, which allows this kind of extreme locomotion without intelligent control.
It was first reported by study's co-senior author Kyu-Jin Cho, the study's co-first author Je-Sung Koh and study co-author Robert Wood in 2013 in the International Conference on Intelligent Robots and Systems.
For the robotic insect to jump off water, the lightweight catapult mechanism uses a burst of momentum coupled with limited thrust to propel the robot off the water without breaking the water's surface.
An automatic triggering mechanism, built from composite materials and actuators, activates the catapult.
To produce the body of the robotic insect, "pop-up" manufacturing was used to create folded composite structures that self-assemble much like the foldable components that "pop-up" in 3D books.
Devised by engineers at the Harvard Paulson School and the Wyss Institute, this ingenious layering and folding process enables the rapid fabrication of microrobots and a broad range of electromechanical devices.
"The resulting robotic insects can achieve the same momentum and height that could be generated during a rapid jump on firm ground - but instead can do so on water - by spreading out the jumping thrust over a longer amount of time and in sustaining prolonged contact with the water's surface," said Wood.
The robotic insect was described in the journal Science.
