How can a snail crawl upside-down on the underside of the surface of a pond?

A water snail can walk on water (so to speak) because it finds the perfect balance between surface tension and viscous drag…

By Deborah Halber

A water snail can walk on water (so to speak) because it finds the perfect balance between surface tension and viscous drag. The creature’s unique propulsion system distorts the water just enough to provide a grip for its slimy “foot.” A land snail, in contrast, propels itself by oozing mucus between its body and its surface of choice – rocks, trees, luxury yachts.  

The snail’s unique propulsion system was illuminated through its first robotic counterparts, RoboSnails I and II, created by MIT mechanical engineers in 2003. RoboSnails consist of electronics aboard a rubber foot that is about six inches long and an inch wide. The robots glide over a thin film of fluid standing in for mucus.

The mini robots were created to test mathematical simulations describing forms of snail locomotion. Land snails “can maneuver over a range of complex terrains—even across ceilings—and they’re very mechanically simple,” said Assistant Professor Anette “Peko” Hosoi of the Department of Mechanical Engineering, principal investigator for the work. They also don’t have exposed joints, so a machine based on their form and covered with rubber resistant to corrosion can navigate in chemically harsh environments.

Besides potentially leading to new forms of locomotion for future machines, the work provides insights into common biological systems. That’s because many systems involve the same general phenomenon behind snail movement: fluid flow contained by a flexible boundary.

Posted: December 16, 2008