This Bio-Inspired Robot Can Jump on Water

Lightweight water striders can glide and jump effortlessly on watery surfaces. Now researchers believe they can rival these insect skills with a simply-designed, low cost robot.

In a study published Thursday in the journal Science, the researchers from Seoul National University and Harvard University describe how their bio-inspired leaping robot. They envision the miniature jumping bots could be used in search and rescue missions and even for for surveillance purposes.

To create the robot, they first used high-speed cameras to study and understand how exactly water striders (Aquarius paludum) leap off water. "By trying to recreate nature, we have to understand the principle behind [a strider's] locomotion," they wrote in a statement. "We cannot just mimic nature. We have to understand the physical principle behind it."

The researchers discovered that the insects' long legs accelerated gradually, preventing the water surface from retracting too quickly and making its legs lose contact with the water. They found that the insects also moved the curved tips of their legs inward in order to extend the amount of time their legs pushed against the water's surface.

In order to mimic these movements in their robot, the researchers recreated the controlled acceleration by using a "torque reversal catapult." This device initially generates a small torque (a twisting force that generates rotation), which gradually builds up. Most importantly, it never goes beyond the water's surface tension force—preventing the robot from sinking.

The researchers' current robo-water strider weighs 68 mg and can only jump once, but leaps to heights of 14.2 cm—which is similar to its organic counterpart.

This isn't the first time that researchers have created water strider-inspired robots. Back in 2012, a team of researchers from China created one that could jump nearly 14 inches forward, despite weighing as much as 1,100 water striders.

On this occasion, the Seoul and Harvard team created a lightweight version that relies on surface water tension to leap (just like organic striders), as opposed to the wide flat paddles employed in the previous attempt.

Although the researchers didn't conduct their research for a set application, they suggested that the technology could potentially be used to make larger robots that can both float and jump on water, or tiny robots that can move around more deftly than more cumbersome bots.

"Instead of using a single large mobile robot or a humanoid, we can use a large number of robots that are small and cheap, which could increase the probability of success," they said.

They explained that these tiny leaping robots could be used in disaster search and rescue missions, environmental monitoring, and even military surveillance purposes.

"An example (although still imaginary) can be found in the movie Minority Report, where many small insect-like robots are deployed in search for a fugitive (Tom Cruise)," they wrote in a statement.

They asserted, however, that they didn't create their robots with stealth missions in mind.

"Of course, we do not want the robots to be used by bad people […] we did not have much intention of putting this robot on the market for those who are looking for surveillance robots in the near future," they said.