A UC San Diego engineer has revealed a new mode of propulsion based on how water snails create ripples of slime to crawl upside down beneath the surface.
Eric Lauga, an assistant professor of mechanical and aerospace engineering at the Jacobs School of Engineering, recently published a paper in the journal Physics of Fluid called "Crawling Beneath the Free Surface: Water Snail Locomotion," that explains how and why water snails can drag themselves across a fluid surface that they can't even grip.
Based on Lauga's research, the secret is in the slime. The main finding of Lauga's research is that soft surfaces, such as the free surface of a pond or a lake, can be distorted by applying forces; these distortions can be exploited (by an animal, or in the lab) to generate propulsive forces and move. Some freshwater and marine snails crawl by "hanging" from the water surface while secreting a trail of mucus. The snail's foot wrinkles into little rippling waves, which produces corresponding waves in the mucus layer that it secretes between the foot and the air.
Lauga and his team demonstrate that water snails have to distort the surface in order to move. "If they don't, they won't go anywhere," said Lauga, who explained that these water snails naturally rise up due to their low weight, and therefore do not have to work to remain near the surface.
Lauga and his colleagues said their finding could lead to a new method of propulsion. One of Lauga's colleagues, Anette Hosoi of the Massachusetts Institute of Technology, has already imitated the adhesive/ lubricating propulsive method of land snails to drive a robotic device. Now, as a result of this new water snail finding, the researchers said it may be possible to build similar devices that walk on water.
"The water snails show us that this is possible, and therefore one can design biomimetic systems taking advantage of that movement," Lauga says.
|Contact: Andrea Siedsma|
University of California - San Diego