Walking on water might sound supernatural, but in fact it is a quite natural phenomenon. Many small creatures use water’s surface tension to maneuver around. One of the most complex maneuvers, 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, emulating this natural form of water-based locomotion, an international team of scientists from Seoul National University (SNU), Harvard’s Wyss Institute for Biologically Inspired Engineering, and Harvard John A. Paulson School of Engineering and Applied Sciences, has unveiled a novel robotic insect that can jump off of water’s surface. They show how natural mechanics allow water striders to jump from rigid ground or fluid water with the same amount of power and height.
“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,”. The water strider, whose legs have slightly curved tips, employs a rotational leg movement to aid it its takeoff from the water’s surface. It took the team several attempts to fully understand the mechanics of the water strider, using robotic prototypes to test and shape their hypotheses.
The best way to jump off of water is to maintain leg contact on the water for as long as possible during jump motion. The robotic insect can exert up to 16X its own body wt on the water’s surface without breaking through, and can do so without complicated controls. Many natural organisms such as the water strider can perform extreme styles of locomotion eg fly, float, swim, or jump on water – with great ease despite a lack of complex cognitive skills. “.. We can learn from this kind of physical intelligence to build robots that are similarly capable of performing extreme maneuvers without highly-complex controls or artificial intelligence.”
METHOD: 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. The lightweight mechanism uses a burst of momentum + 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, was employed to activate the catapult.
For the body of the robotic insect, “pop-up” manufacturing was used to create folded composite structures that self-assemble. This ingenious layering and folding process enables rapid fabrication of microrobots and a broad range of electromechanical devices.
http://wyss.harvard.edu/viewpressrelease/210/
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