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November/December 2006  |  VOLUME 117, NO. 6
Praxis
Slime power
Fast. Efficient. Powerful. And slimy.

A snail's pace
A snail's pace: Snails have three modes of locomotion: forward undulating motion, backward undulating motion, and galloping.
Brian Chan and Anette Hosoi

That’s the kind of snail Jon Wilkening wants to design. A sleek, shapely robotic snail that can move at the speed of — well, a bit faster than your typical slug.

At a conference, the Berkeley mathematician saw a demonstration of MIT professor Peko Hosoi’s Robosnail. About the size and shape of a belt sander, the robot quivered and vibrated its flexible foot, creeping jiggle by jiggle to the other side of a bed of silicon oil.

He approached Hosoi after the talk. "I bet we can make that thing go faster," he said.

A snail named Archie holds the high-speed record of the Guinness Gastropod Championship in London. Archie slid across the 13-inch course in only 2 minutes and 20 seconds. The average garden snail travels at a speed of 23 inches per hour.
Chris Barron, Courtesy of Hambleton District Council

Hosoi took him up on it. She and her graduate student Brian Chan had built the snail to understand how films move across fluids, never thinking a robotic snail might actually be good for something. But then she received a phone call from Schlumberger, a British company that explores for oil. They needed a robot to slither down oil wells to perform tests. One that could wriggle through oil and gunk. Something extremely robust that would never get stuck, ruining a well. A snail would be perfect, but — it’d be nice if it went a bit faster.

Wilkening was the man for the job. A snail moves by sending waves along its foot, and Wilkening investigated the best shape for those waves. The Robo-snail uses smooth waves curved like ocean swells on a calm day, but he used mathematical equations to design a better method. Waves that were pointy, like choppy seas in a storm, would send the snail careening along at least 50 percent faster, by his calculations.

Now Hosoi is designing a new robot to test out Wilkening’s theory. But, she says, there’s only one way to determine which Robosnail design is faster: a slime-off.