Inspired by water striders: self-unfolding fans make the ‘Rhagobot’ agile
Water strider fans inspire mini robots. The technology is designed to enable lightning-fast maneuvers on water.
"Rhagobot" – a robot in the shape of a water strider
(Image: Georgia Tech College of Engineering)
An international research team has deciphered how the water strider species Rhagovelia uses tiny, fan-like structures on its legs to maneuver at lightning speed even in torrential streams – and successfully transferred this principle to a microrobot. The study was published in the journalScience.
The insects, which are only the size of a grain of rice, do not use muscle power, but only surface tension and elastic forces to open and retract their ribbon-like compartments in fractions of a second. This mechanical, passive movement is ten times faster than the blink of an eye. This enables the insects to glide over the surface of the water at up to 120 body lengths per second and make turns in just 50 milliseconds. In doing so, they create flow patterns that are reminiscent of the swirl marks of wings in the air, as described in the paper.
From insect to robot
In order to make this natural principle technically usable, the researchers developed a self-deploying elastocapillary fan weighing just one milligram and integrated it into an insect-sized robot – the "Rhagobot". The mini-robot can now accelerate, brake and maneuver sideways on its own. There is no need for a complex energy supply or complicated controls. "Our robotic fans fold themselves – using only water forces and geometry," says Je-Sung Koh, professor at Ajou University. "This is a form of mechanical intelligence that evolution has perfected over millions of years."
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The research was carried out jointly by teams from the University of California, Berkeley, the Georgia Institute of Technology and Ajou University in South Korea over a period of more than five years. The decisive discovery was made when the team used a scanning electron microscope to examine the microstructure of the fans. The analysis revealed that the fans of the insects are structured like flat ribbons. This means they can be folded up quickly and still remain stiff enough to generate propulsion – a property that made the robotic design possible in the first place. The researchers envision possible application scenarios for such robots in the form of semiaquatic micro-robots that could be used in turbulent currents, flood plains or for environmental monitoring.
(mack)
