Snake-like robots have been built before, but they tend to use a lot of power and typically require a lot of hardware to control of each segment. Hamid Marvi, a Mechanical Engineering PhD candidate, videotaped 20 different snake species to figure out if there was a way simplify existing designs.
Snakes lift the scales on their underside and pull themselves forward by sending a muscular traveling wave from head to tail — if you watch a big snake move you can see a sort of pulse move down its body. Another useful aspect to the movement is the snake doesn't need to bend its body in order to move.
A robot that could do this would use a lot less energy, as well as being better able to slip through small spaces. That's important because a snake-like 'bot would be perfect for a search-and-rescue mission — perhaps finding someone under a pile of rubble.
Marvi built the Scalybot to do just that. Scalybot 2 can change the angle of its scales depending on the terrain or the slope. That allows it to pull itself along in the same way snakes do. It doesn't look much like a snake, and the motion is still clunky, but it can do what snakes can do, which is adjust how much friction it has with a surface. The "scales" on the bottom can change the angle they touch a surface at, according to whether the robot needs to slide or hang on. Given that a search-and-rescue robot would need to handle a wide range of surfaces at many different angles, that's an important feature.
Image: Georgia Tech