The breakthrough was possible thanks to a high-end printer that allowed researchers to print soft and rigid materials together within the same components. This made it possible for researchers to design more complex shapes for the robot's legs. The legs are made up of three parallel, connected sealed inflatable chambers, or actuators, 3-D-printed from a rubber-like material. The chambers are hollow on the inside, so they can be inflated. On the outside, the chambers are bellowed, which allows engineers to better control the legs' movements. For example, when one chamber is inflated and the other two aren't, the leg bends. The legs are laid out in the shape of an X and connected to a rigid body.