Self folding 3D origami robot can swim, climb & walk

Measuring about a centimeter from front to back, the entire walking motion is embedded into the mechanics of the robot body. The origami robot design was motivated by a hypothetical application in which tiny sheets of material would be injected into the human body, navigate to an intervention site, fold themselves up and, when they had finished their tasks, dissolve.

All the prototypes were built from liquid-soluble materials. One prototype robot dissolved almost entirely in acetone, while another prototype's components were soluble in water. The self-folding sheets had three layers, throughout all the prototypes and the final design. The middle layer always consisted of polyvinyl chloride, which contracts when heated. In the acetone-soluble prototype, the outer layers were polystyrene.

To help the folding process, slits were cut into the outer layers of the robot with a laser cutter. The researchers discovered that if two slits of different widths are on opposite sides of the sheet when the middle layer contracts, it will force the narrower slit's edges together, resulting in the sheet bending in the opposite direction. The sheet will begin folding at around 65ºC.

After the 3D robot has folded itself up, the body flexes due to the application of a magnetic field to the permanent magnet on its back. The friction between the robot’s front feet and the ground is great enough that the front feet stay fixed while the back feet lift. The robot’s body then twists slightly due to another sequence of magnetic fields, which breaks the front feet’s adhesion and causes the robot to move forward.