Last year, the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) developed a soft robot using a flat kirigami sheet that transformed uniformly when stretched.
Now SEAS has developed an improved version of the snake-inspired soft robot that is faster and more precise than its predecessor.
This robot is also made using kirigami — an ancient Japanese paper craft that relies on cuts to change the properties of the material. As the robot stretches, the surface “pops up” into a 3D-textured surface that grips the ground like a snakeskin allowing it to move.
"This is a first example of a kirigami structure with non-uniform pop-up deformations," said Ahmad Rafsanjani, a postdoctoral fellow at SEAS. "In flat kirigami, the pop-up is continuous, meaning everything pops at once. But in the kirigami shell, pop up is discontinuous. This kind of control of the shape-transformation could be used to design responsive surfaces and smart skins with on-demand changes in their texture and morphology."
The new soft robot design combined two properties of the material: the size of the cuts and the curvature of the sheet. Controlling these features allowed researchers to program dynamic propagation of pop-ups from one end to another.
The kirigami surface is rolled into a cylinder with an actuator applying force at two ends. If the cuts are consistent size, the deformation propagates from one end of the cylinder to the other. If the cuts are chosen carefully, the skin can then be programmed to deform at desired sequences.
The next steps are to develop an inverse design model for more complex deformations. So if the skin can transform, the structure can just cut, roll and go, researchers said.
The full research can be found in the journal Proceedings of the National Academy of Sciences.