Tropes

www.sci-news.com 2015 00770.txt.txt

#Researchers Create Robotic Water strider A team of researchers and engineers, led by Dr Kyu-Jin Cho of Seoul National University in Korea, has created an insect-like robot that can jump on water surfaces. As Dr Cho and co-authors watched the water strider jump on water surfaces using high-speed cameras, they noticed that the long legs accelerate gradually, so that the water surface doesn retreat too quickly and lose contact with the legs. Using a theoretical model of a flexible cylinder floating on liquid, the scientists found that the maximum force of the water striderslegs is always just below the maximum force that water surface tension can withstand. They used a torque reversal catapult mechanism that generates a small initial torque and gradually increases but that never exceeds the surface tension force of water. As well, the high-speed cameras reveal that the water strider sweeps its legs inward in order to maximize the time the legs can push against the surface of the water, thus maximizing the overall force; this additional concept was applied also to the robots to help them achieve lift off. umping on water is a unique locomotion mode found in semiaquatic 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, the scientists wrote in a paper published in the journal Science. e 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). With sufficiently light weight, long limbs, and the proper physical mechanisms, the robots developed by Dr Cho and his colleagues effectively mimic their inspirational counterparts in nature. e built a 68-milligram at-scale jumping robotic insect and verified that it jumps on water with maximum momentum transfer, the scientists said t

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