"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," said the study's co- first senior author Kyu Jin Cho, director of the Biorobotics Laboratory at Seoul National University. "The water strider is capable of doing all these things flawlessly."
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. Many natural organisms such as the water strider can perform extreme styles of locomotion - such as flying, floating, swimming, or jumping on water - with ease despite a lack of complex cognitive skills.
"This is due to their natural morphology," said Cho. "It is a form of embodied or physical intelligence, and we can learn from this kind of physical intelligence to build robots that are similarly capable of performing extreme manoeuvres without highly-complex controls or artificial intelligence."
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.
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, was employed to activate 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.
Robert Wood, Ph.D., co-author on the study and founder of the Harvard Microrobotics Lab, concluded. "The resulting robotic insects can achieve the same momentum and height that could be generated during a rapid jump on firm ground by spreading out the jumping thrust over a longer amount of time and in sustaining prolonged contact with the water's surface."
