Researchers have designed and built a tiny robot that not only walks on water, but leaps free from its surface, talents that mimic the water strider. The insects are so light they ride high on the water’s surface, and they use the especially hairy feet on their middle set of legs to row their way across the water. Previously, engineers have designed striderlike robots that can walk on water, too, but they’ve never been able to duplicate the insect’s ability to jump and escape (first 9 seconds of video, above)—until now. The new bugbot is about twice the size of a water strider and tips the scales at just 68 milligrams, a small fraction of the weight that water’s surface tension can support on an area that size, the researchers report online today in Science. Just like its insect role model, the robot uses four legs to propel its leap from either a solid surface or from water—but it does so using the energy stored in a spring-loaded device that mimics the action of a flea’s leg when it jumps. This heat-activated spring is fine-tuned so that it pulls the bugbot’s flexible, curved-at-the-tip legs inward and downward at a speed just below that that would pierce the water’s surface (last 15 seconds of video), thus producing a successful leap rather than a flailing flop. A superrepellent coating on the robot’s feet and legs help prevent the water from slowing down its ascent. Although the bugbot’s body rests just 1 centimeter above the water’s surface and its legs are just 5 centimeters long, it can leap to a height of more than 14 centimeters, the researchers note. During test jumps, the robot briefly experienced accelerations of about 13.8 g—more than three times those stomached by astronauts on the space shuttle as they were boosted into orbit. Results of the new study may help engineers design bugbots that could be deployed in swarms for environmental monitoring, search and rescue operations, or the surreptitious surveillance of an enemy.
(Video credit: Seoul National University;(Video editor) Sarah Crespi/Science)