From snake-like machines designed to have sex with your car, to metal cheetahs that can outrun a cyclist, there’s certainly no shortage of animal-inspired robots – and for good reason. There’s nothing quite like having billions of years of evolution in your arsenal when you’re trying to solve a problem like, say, how to jump on water.
This was the driving force behind the latest collaboration between Harvard’s Wyss Institute for Biologically Inspired Engineering and Seoul National University: a tiny robot that not only can move across the surface of water, but jump on it with the same force and speed that it does on land.
The design for the bot was inspired by water striders, a group of aquatic insects in the family Gerridae. “Many small living creatures leverage water’s surface tension to maneuver themselves around,”says the Harvard team. Take the pygmy gecko, which is small enough to drown in a raindrop, yet walks on water with ease. “But in order to achieve jumping, water’s surface needs to be pressed at just the right speed for an adequate amount of time, up to a certain depth.”
Because of this complicated cohort of stipulations for a successful aqua-jump, few animals or engineered machines have achieved it. “But the water strider is capable of doing all of these things flawlessly,” explains senior team member Kyu Jin Cho. “This is due to their natural morphology. 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 maneuvers without highly complex controls or artificial intelligence.”
Using a high-speed camera, the team carefully analyzed the striders’ jumps, and made an interesting discovery in the process. Not only does the tiny insect exert the maximum amount of force possible without breaking the water’s surface, but they do this steadily and gradually.
“When you apply too much force at once, the legs pierce the surface, and you don’t get much of anywhere,” says Cho. But a set of curved legs which rotate on takeoff keep the strider in contact with the water over a longer period of time, allowing a slower buildup of thrust.
“We were able to reveal the core principle needed to jump on water at the scale of an insect,” the team wrote in a press release. “[Now], this robotic tool can help deepen the understanding of how the insects and animals move.”
The final thumb-sized bot relies on a lightweight catapult mechanism that snaps shut via a heat-reactant spring zapped by a pulse of heat. It can launch itself 5.5 inches (14 cm) into mid-air, and exerts 16 times its own body weight without puncturing the water.
Some commenters have compared the hoard of mechanical striders to the nightmare-inducing spider bots we watched “The Cruise Missile” contend with in Minority Report. And while this particular batch isn’t equipped with retina-scanning tech, surveillance applications aren’t completely out of the question. More importantly, mastering the various terrains on our planet – and now other planets – remains a key challenge for robotics. This might look like one tiny jump for a bug-bot, but we could be watching the start to a big jump for mankind.