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MIT Scientists Build Robotic Snail

Posted on: Tuesday, 15 July 2003, 06:00 CDT

The slimy trail that snails and slugs putter along has long puzzled biologists. How is it that the creatures move along the goo - the thicker the goo, the faster they go, while a thinner trail of the stuff offers more resistance? Massachusetts Institute of Technology researchers fascinated by those questions have built what might be the world's first robotic snail to study a matter that ultimately could lead to advancements in the medical world to allow doctors to provide more targeted treatment for cancer.

The project carries a twofold purpose: first, to understand how the snail's mode of locomotion works, and secondly, to observe how liquids behave at a very small scale, a field known as microfluidics.

"People have looked at the properties of slime in the past, but more from a biological point of view, not from the engineering angle," said Anette Hosoi, an assistant professor of mechanical engineering at MIT. "So now we've begun to take a look at the mechanical side of the biology. It's like walking. It's a mechanical act, but not everyone has been concerned with the biology behind it."

To ponder the slime, Hosoi, graduate student Brian Chan and fellow assistant professor John Bush spent several weeks putting together a mass of unsophisticated gears, wiring and pieces of plastic to build a robotic snail. It measures about 10 inches in length and is housed in a rubbery membrane that moves forward on a thin layer of slime.

"It's very much $5 science," Hosoi said.

Two forms of artificial lubricant have been tried: silicon oil, and a mixture of glycerin and water. The slippery stuff produced by real snails is known as a non-Newtonian fluid, whose viscosity depends on the amount of force applied.

"We are good at building things that move on flat surfaces, but it would be useful for things to go over all terrains. We're using this robotic snail to gain an understanding of how to do that," Hosoi said.

But why study something so ... gross?

"If you want to build something that moves over all terrains, it's better to build it small. A snail has a couple of advantages in this area: It has one foot, it's small and it can go over anything," Hosoi said.

Although the project is not directly involved with medical science, Hosoi says there is hope it could lead to advances in the field, particularly in one aspect known as "lab on a chip." Just as silicon chips revolutionized computer electronics, the "lab on a chip" may spawn miniaturized machines or methods for providing medical treatment.

The robotic snail could play a key role in the drive toward smaller devices.

Todd Thorsen, an associate professor of mechanical engineering at MIT, says the lab on a chip's technology shrinks everything.

"Functions typically done by bulky diagnostic equipment are brought down onto a single, addressable, postage-stamp-sized chip. This saves money, space, labor and time," he says while also warning against getting "caught up in the science fiction aspects of this."

"There are a lot of possibilities not only in this area, but also for analyzing DNA and RNA in diagnosing diseases or outbreaks of food contamination like salmonella," Thorsen said.

He says there are a number of applications that could be applied to preventative medicine, including "addressable channels and sensors that can measure dozens of compounds in human blood simultaneously from a finger prick-sized sample."

Thorsen admits there are a number of challenges in the future, but he feels that there have been great advances in microchip technology over the past five years, some of it already being marketed.

While two fellow students in Hosoi's lab try to better understand the movements of "Robosnail," Chan has kept busy. He traveled to California to study the movements of the banana slug, a large yellow beastie that can grow up to eight inches and can provide a good view of how slugs move. And he is working on a smaller version of the mechanical snail to further study locomotion.

"This one will undulate forward in waves," Chan says. "It's like a long carpet with kinks. You remove the kinks by pushing it along, forcing the carpet to move forward."

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