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Artificial system replicates biological movement

Vid Scientists have created a leggy microrobot that mimics the actions of a water strider.

They wanted to replicate the movement of the semi-aquatic insects to try to have a better understanding of how they are able to jump from watery surfaces with the same amount of force and height as a leap from rigid ground.

Boffins from Seoul National University (SNU) in Korea, Harvard's Wyss Institute for Biologically Inspired Engineering and the Harvard Paulson School of Engineering and Applied Sciences published their findings in the Science journal on Friday.

Robot prototypes were produced using a manufacturing technique, known as Pop-up MEMS, that enables complex 3D machines – such as Harvard's RoboBee – to be developed in the mesoscale.

They studied how water striders use their long, curve-tipped legs as a rotational device to help the insects lift off with ease from the water's surface.

Co-senior author of the paper, Kyu Jin Cho, who is associate professor in the Department of Mechanical and Aerospace Engineering and director of the Biorobotics Laboratory at SNU, said that the water's surface needed to be "pressed at the right speed for an adequate amount of time, up to a certain depth, in order to achieve jumping."

He added: "The water strider is capable of doing all these things flawlessly."

There was plenty of trial and error along the way, we're told, as the scientists attempted to build a robot that replicated those actions. They found that the smoothest way to jump off of water involved maintaining leg contact on the fluid surface for as long as possible during the locomotion.

"Using its legs to push down on water, the natural water strider exerts the maximum amount of force just below the threshold that would break the water’s surface," said the co-first author of the paper, Je-Sung Koh, who is a Postdoctoral Fellow at the Wyss Institute and the Harvard Paulson School.

The robotic insect produced by the engineers was able to exert up to 16 times its own body weight on the water's surface without breaking through.

Wyss Institute founding director Donald Ingber said:

This international collaboration of biologists and roboticists has not only looked into nature to develop a novel, semi–aquatic bioinspired robot that performs a new extreme form of robotic locomotion, but has also provided us with new insights on the natural mechanics at play in water striders.

The water strider research, perhaps unsurprisingly given the resultant microrobot's potential uses, received funding from South Korea's Defense Acquisition Program Administration. ®

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