'Robosnail' reveals the wonders of goo
MIT scientists try to unlock the medical secret of slime
Wednesday, July 16, 2003 Posted: 10:29 AM EDT (1429 GMT)
Scientists hope the robotic snail will help them figure out how gooey creatures get around, and also advance the study of how liquids behave at a very small scale.
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.
-- Anette Hosoi, MIT professor
CAMBRIDGE, Massachusetts (AP) -- 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.
Studying motion, fluids
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.
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 (25 centimeters) 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.
Trying out different fluids
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.
Pushing for smaller
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."
Smaller snail in the works
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 (20 centimeters) 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.
MIT scientists copy the snail's pace
Robot to be used in fluids research
By Gareth Cook, Globe Staff, 7/3/2003
CAMBRIDGE -- Scientists at MIT have created what they believe is the world's first robotic snail, a humble collection of gears, wiring, and a rubbery membrane that creeps forward on a thin layer of gooey slime.
The robot was built to help scientists learn how snails and slugs manage to push themselves along on their slime trails, a method that puzzles biologists despite years of scrutiny. On a larger front, however, the snail is the latest -- and perhaps strangest -- development in the booming field of ''microfluidics,'' which is the science of understanding how liquids behave on a very small scale.
Just as engineers revolutionized electronics by miniaturizing them on silicon chips, scientists are racing to find ways to control the movement of tiny amounts of fluid -- the key to remarkable chips with applications as diverse as finding new cancer drugs, or building a portable biological weapons detector.
''This is important because microfluidics is becoming so important,'' said MIT's Anette Hosoi, standing over the Robosnail as it moved across a tray of glycerin.
The snail, built by MIT graduate student Brian Chan under the direction of Hosoi and another professor, is a 10-inch long prototype that can currently move only on horizontal surfaces. In the future, the team hopes to build an ''all-terrain'' model that can scale inclines and maybe even walls.
What interests researchers isn't the prospect of an automated garden pest, however, but the science of its slime trail.
For past several years, researchers in the snail lab and elsewhere have made great strides in making chemical reactions happen on smaller and smaller scales. At the moment, the main interest among scientists is to devise ways to build a ''laboratory on a chip,'' with a system of tiny pipes, mixers, heaters, and detectors.
Already, California-based Caliper Technologies Corp. sells microfluidic chips to drug companies that need to quickly check the effects of compounds on a biological process behind a disease. But the goal is to make a wide range of chemical and biological reactions cheap and easy, so an inexpensive detector could look for the presence of anthrax, or quickly do a battery of standard blood tests.
''The blood sample will no longer be sent to a lab,'' said Abe Stroock, an assistant professor of chemical and biomolecular engineering at Cornell University. ''The doctor will do the analysis while you sit there, with a hand-held device.''
All these technologies are beset by a consistent problem: As engineers shrink everything down, liquids start to behave strangely. The smaller the scale, the more ''sticky'' a liquid seems to be -- a fact familiar to anyone who has witnessed a bead of water stay in place on a window. In a pipe the size of a human hair, water moves like honey, sticking to the sides and trapping things that try to move through it. So Massachusetts Institute of Technology researchers decided to engineer their own version of an animal that thrives on stickiness to discover more about what it takes to move in this strange environment.
To understand something of the snail's secret, imagine moving a finger on a plate thick with maple syrup. The thinner the layer of maple syrup, the harder it is to move a finger back and forth.
Robosnail creates a series of slow waves along its rubbery bottom. Where the wave pushes down the most, and the sticky fluid is thinnest, the fluid resists being pushed back the most. Just behind each wave, an area of high-pressure liquid forms, effectively giving Robosnail toeholds to push forward, said Hosoi, who is an assistant professor of mechanical engineering. Understanding this better could allow scientists to design a better swimmer for a microfluidic environment, or just have a firmer grasp on how a flexible membrane (like a cell wall) interacts with the environment.
The quirky project is an example of how engineers are looking to nature as they devise ways to radically shrink machines. Scientists in California are trying to mimic the flight principles of the house fly so they can build very small flying drones. Other scientists have suggested that the swimming techniques of bacteria could be copied for a submarine so small it could maneuver through a human capillary.
Elsewhere, researchers are tackling other stubborn questions of microfluidics. One vexing issue, for example, is how to quickly mix two liquids when both move slowly, like honey and molasses. Cornell's Stroock recently published a paper describing an ingenious method he devised. Inside the tiny tube where the fluids are to mix, he etched grooves along the side like those used inside the barrel of a rifle, causing the fluids to roll and knead into each other.
Another recent paper, from a team at California Institute of Technology, described a way to build a hundreds of chambers and thousands of pipes and valves, all in an array smaller than a hand -- the beginnings of the kind of large-scale miniaturization used to make computer chips.
Hosoi's graduate student, Chan, is currently on an expedition to California to collect banana slugs -- bright yellow slugs that can exceed half a foot in length -- so the team can study how slugs move in greater detail. Two other students in Hosoi's lab are spending the summer trying to understand how exactly Robosnail moves, and how it could be optimized -- mathematical problems that could have more general implications in microfluidics.
Hosoi said she doesn't see much commercial application for Robosnail, though a future version might be able to repair a machine covered in oil.
''You would definitely have to have it in a setting where you don't mind a trail of something behind it,'' she said.