The robot doesn't have a hard internal skeleton; it is composed solely of elastomeric polymers and a series of chambers. Using a pneumatic valving system, the chambers can be inflated to create movement, which boils down to a combination of crawling and undulation.
All of this enables the 5-inch robot to crawl, for example, under a glass plate elevated 2 cm from the ground. In a series of tests, scientists were able to navigate the robot through that gap in under a minute.
This type of design makes the robot less susceptible to damage from falls and colliding with hard objects. It does, however, makes it more susceptible to damage from punctures.
Another drawback is the problem of power: the robot is connected to an external power source, which won't do in real world situations. “There are many challenges to actively moving soft robots and no easy solutions,” neurobiologist Barry Trimmer, one of the designers of the robot, said in an email to the Washington Post.
Check out a series of videos and a PDF detailing the design of the robot here.