Robot Walks on Water

Mimicking Insects to Avoid Sinking

Using Surface Tension

July 1, 2006 — A new robot made of ultralight carbon-fiber can stand or slowly walk on water. The principle it uses is borrowed from insects — surface tension tends to prevent the water’s surface from breaking, and the robot’s legs from sinking in.


PITTSBURGH — Nature inspires many things, from fashion to perfume to furniture. Now, technology gets a little inspiration.

After watching tiny bugs like these walk on water, Carnegie Mellon University mechanical engineer Metin Sitti wanted one of his own.

“We tried to make a robot to simulate the insect,” he tells DBIS. He tried and succeeded. This new tiny, lightweight, spindly legged creature is a robot that can propel itself across water in all directions. It can turn even sharp corners like the insect does, so it’s very agile.

The robot’s body is made of a super-light carbon fiber material. Its steel legs are coated with non-stick Teflon to repel water. A tiny battery gives it power.

“Right now we move by five centimeters per second, and the real insect can go up to one meter per second. So we are like around 20-times less speed,” Sitti says.

It might be slower, but just like insects, the robot doesn’t float. It stands on top of water thanks to the physics of surface tension. The surface is so strong that the robot’s feet only dent the water without breaking the surface while supporting the weight of the robot without sinking.

“When they put their legs on the surface of the water surface, they repel each other,” Sitti says. “And that repulsion can lift the body because it’s so light bodyweight.”

In the near future, Sitti says his creation could carry sensors to detect toxins in water supplies. “We can make many of them, like tens or hundreds of them, and cover a wide range and give you constant, continuous, water quality report,” he says.

Researchers have already received interest in the robot as an educational toy, to educate students and the public about water surface effects, and to provide entertainment.

BACKGROUND: Researchers at Carnegie Mellon University have built a tiny robot that can walk on water, much like insects known as water skimmers, water skaters, pond skaters or Jesus bugs. Although it is still a prototype, its creators believe it could one day be equipped with biochemical sensors that monitor water quality. It could be used with cameras for spying, search and rescue operations, or for exploration. The robot might also be outfitted with bacteria to help break down pollutants in the environment.

THE JESUS LIZARD: In 2004, Harvard researchers discovered how basilisk lizards (sometimes called “Jesus lizards” because they appear to walk on water) manage to run across the surface of water on their two hind legs, with front arms outstretched. They move at speeds faster than 1.5 meters per second, comparable to a human running 65 MPH. The lizard first slaps the water with its web-like foot, strokes downward with an elliptical motion to create an air pocket, and then pulls its foot out of the water by curling its toes inward. By repeating this sequence up to 10 times a second, it generates sufficient forward thrust and lift to run on water without tipping over or sinking.

WHAT IS BIOMIMICRY: Biomimicry is a field in which scientists, engineers, and even architects study models and concepts found in nature, and try to use them to design new technologies. It as a design principle that seeks sustainable solutions to human problems by emulating nature’s time-tested patterns and strategies. Nature fits form to function, rewards cooperation, and banks on diversity. For instance, the Eastgate Building in Harare, Zimbabwe, is the country’s largest commercial and shopping complex, and yet it uses less than 10 percent of the energy consumed by a conventional building of its size, because there is no central air conditioning and only a minimal heating system. The design follows the cooling and heating principles used in the region’s termite mounds.

The Institute of Electrical and Electronics Engineers, Inc., contributed to the information contained in the TV portion of this report.

Sourced & published by Henry Sapiecha


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