Nature.com is reporting today that researchers from MIT have created a robotic snail capable of climbing vertical walls and traveling upside down across ceilings. The team, led by Anette Hosoi, developed the mechanical slug primarily to study the locomotive mechanisms of biological snails, although they believe the results of their research will eventually end up in practical robot applications.
Like worms, land snails move by alternatively contracting and stretching their bodies. A snail has a single foot on the underside of its body that has a thin layer of sticky mucus between itself and the ground (or whatever surface it is on). The mucus aids locomotion in several ways. It protects the sensitive foot from being injured by the terrain, it reduces friction, and it helps to hold the snail in place while the muscle in its foot contracts from front to back during movement. When the contraction reaches the front of the snail, contact between the snail and the surface is broken at the front allowing the snail to stretch out to its full length, moving the whole snail forward slightly. By repeatedly contracting and stretching, the snail inches ahead at a pace that is infamously slow.
While not modeling the snail body and foot exactly, the MIT team has developed a robot whose mechanism of movement reflects the contraction/stretching cycle pretty closely. The robot itself sits on a “foot” consisting of five movable segments attached to a track on the underside of the robot. Starting at the back, each segment moves forward individually followed, in turn, by the segment in front of it. When the front-most segment has completed its advance, the body slides forward on its track, repositioning itself over the segments so that the process can begin again. The artificial mucus is a clear sticky gel made by mixing a special clay, Laponite, with water. The gel is not made or put down by the robot itself, but rather researchers covered the path of the robot with 1.5mm-thick layer ahead of its advance.
Regardless of these small differences, the researchers were able to prove this system to be an effective means of moving the robot. It was placed on a flat plane, and as the robot began moving forward the platform was slowly inclined. There were no decrease in its performance as the steepness of the surface increased even to the point of being vertical. At one point the platform was flipped upside down and the robot continued its advance unimpeded. Of course there was a lot of research done ahead of time in order to determine the optimal combination of robot weight and gel concentration (for stickiness).
Although the artificial snail’s movement process is slow and messy, the scientists predict that there do exist applications for snail-like robots. Their ability to crawl up and over most objects makes them very well suited for many diverse environments and terrains. Hosoi and her team are taking what they have learned from this project and beginning to plan for the next generation of snail robots, which they hope will be able to move faster and be more maneuverable.
This is not the first robot to try to simulate muscle contractions and expansions as a way to drive movement. The Amoeba bot created by Dennis Hong at Virginia Tech is based on similar principles although its mechanical representation is fairly different than MIT’s.
The MIT research was published in the November 2005 issue of Physics of Fluids.
Read the full article on Nature.com: “Who wants a slugbot?“