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Gecko foot

VIDEO: Robert Full shares the secrets locked in geckos' toe hairs.

Video: Robert Full tells why copying hairs on geckos' toes might eclipse the invention of Post-Its and Velcro - low bandwidth   1:18 / 896KB
Video: Robert Full tells why copying hairs on geckos' toes might eclipse the invention of Post-Its and Velcro. - low bandwidth   1:18 / 2.4MB

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PEDALing into the Future: Three applications

Gecko-inspired adhesive

Closeup of the tiny hairs, or setae, on a gecko's toe.
Closeup (magnified 700 times) of the tiny hairs, or setae, that line geckos' toes.

 

The branches, or spatulae, on the end of a single gecko seta.
The branches, or spatulae, on the end of a single gecko seta, magnified 30,000 times.

Photographs by Kellar Autumn, an assistant professor of biology at Lew & Clark College and former UC Berkeley graduate student who is now a collaborator with Full.
 

How geckos manage to walk on walls and across ceilings has been a mystery for many years. Some scientists speculated that the lizards' feet relied on a layer of water whose surface tension created sticking power. But working in the PolyPEDAL Lab, Full gained a greater knowledge of the structure of a gecko foot, which has millions of microscopic hairs (called setae) on its bottom. These tiny setae span just two diameters of a human hair, or 100 millionth of a meter, and each seta ends with 1,000 even smaller pads at the tip.

As they announce in an forthcoming journal article in the Proceedings of the National Academy of Sciences, Full and other researchers from Lewis & Clark College, UC Berkeley, UC Santa Barbara and Stanford University have developed synthetic copies of the tip of one of these microscopic hairs, using two different materials. By doing so, they have ruled out water adsorption as the source of the sticking power, concluding that the setae instead take advantage of Van Der Waals forces (weak intermolecular attraction) to adhere temporarily. (For details, read the press release.) "We confirmed it is geometry, not surface chemistry, that enables a gecko to support its entire body with a single toe," says Berkeley engineering professor Ron Fearing. That means the adhesive can be made out of any material.

Why so much fuss over a gecko toe? It turns out that when grouped together, these setae could outswing Spider Man. A single seta can lift an ant a hundred times the seta's weight. A million setae, which could easily fit onto the area of a dime, could lift a small child. And it could do this without leaving a residue, latching on faster and more easily than Velcro.

A dry, self-cleaning adhesive like this would have many commercial applications. The team has filed patents and is partnering with several companies to develop a reusable adhesive material that could be applied in a number of ways, from transporting semiconductor chips through a factory's vacuum chamber (using suction devices can scratch the chips), to moving fiber-optic pieces through the human body for surgery and attaching equipment to the exterior of a space station. Or, artificial setae could help build the most mobile robot yet — unfazed by slippery vertical surfaces and able to hang from the roof by a single hair.

Artificial muscles

The self-stabilizing principles identified by Full have changed the way researchers think of artificial muscles, whether as part of a robot or a future human prosthetic.

Early artificial limbs have resembled unwieldy Terminator-strength steel joints with wire tendons. To move in concert, these limbs have been computer-guided. But as it turns out, it's possible to get a two-legged robot with artificial muscles to walk without a brain, merely by making its muscles out of a flexible, springy material and setting the tension carefully.

"If you set the muscles right, so that just as the leg extends, it stretches the muscles a little bit to stop the motion, and then if you time it right to sit it back down, you can get remarkable stability," says Full.

Full is working with SRI International to see if simple pieces of acrylic or silicone, when activated appropriately, will operate in the same fashion as real muscles do. In the future, "instead of having all those separate parts and a big motor that runs them — something you attach to a prosthetic, for example — you'll have something more lightweight," says Full. "At a joint right now, a single motor pretty much dominates the whole joint. Eventually you'll be able to put 10, 20 artificial muscles together and have much more sophisticated control."

Robots

Forget the Jetsons and their robot maids. Full is more interested in what thinking machines can do to help humans in distress. "One of the things we hope robots will be useful for is search and rescue," he says. "A small, multilegged robot should be able to go into a troubled area, whether the result of an earthquake or bombing, and search for individuals. Imagine a swarm of insects quickly going in to check for life." The PolyPEDAL Lab is working with engineers to integrate antennae, eyes and sensors that feel and detect heat into the current crop of robots. Ariel, developed by iRobot in collaboration with Full, can already locate mines lying on the sandy surface of the surf zone. Future ant-sized robots, similar to ones that Berkeley engineering professor Kris Pister is working on, could perform microsurgery.

In the near term, Full sees robots and robotic devices extending the reach of the electronic world. "We can already see other places remotely, through the Internet," he says. "What if we could actually do things there? Robots could give the Internet legs and hands."

 
 
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