The spider robots that invade the bath of Captain John Anderton, played by Tom Cruise, were one of the highlights of iconic 2002 film Minority Report. Now a team of international researchers has created a similar insect android that can launch itself easily from the water.
“I‘m just fascinated by how the water striders can jump on water and I‘m really excited to see that we were able to extract the principles from nature to re-create one of the most fascinating locomotion of nature, the water jumping,” said Kyujin Cho, professor of mechanical engineering at Seoul National University.
The prototype robot weighs just 68 milligrams and has a two centimeter long body.
The researchers from Seoul National University and Harvard University, studied how water striders (Gerridae) jumped on water, to create a robot that could successfully launch itself from the surface of water. They noticed that the creature’s long legs accelerate gradually, so that the water surface doesn’t retreat fast and lose contact with the legs.
The authors theorized that the maximum force of the striders’ legs is always just below the maximum force that water surface tension can withstand. In their robot they used a torque reversal catapult (TRC) mechanism to generate a small initial torque and gradually increase, without exceeding the water’s surface tension.
High-speed camera footage of the insects also revealed that the water strider sweeps its legs inward to maximize the time they can push against the surface of the water, thus maximizing the overall momentum. They then applied this concept to help them achieve lift off.
If the water surface is not broken, it can endure 16 times the body weight of the robotic jumping insect. The robotic insects can jump as high on water as on hard ground.
In addition to Cho, the multi-disciplinary research team included biologists Professors Piotr Jablonski and Sangim Lee and fluid dynamics Professor Ho-Young Kim, all from Seoul National, and Harvard biorobotics Professor Robert Wood.
Their work is published in the journal Science on July 31.