Battery and wire-free robots fold like origami

Folding robots, based on the ancient Japanese art form of origami, have been emerging as a field of convenient robotic design. In origami, a flat sheet of paper is creased and folded to create a complex, three-dimensional shape.

However, robots generally require batteries or wired connections to external power sources, rendering them too bulky for folding. The researchers – based at Harvard’s Wyss Institute for Biologically Inspired Engineering and the School of Engineering and Applied Sciences (SEAS) – aimed to design an origami-inspired robot which did not have its functionality limited by batteries or wires.

“Like origami, one of the main points of our design is simplicity,” said co-author Professor Je-sung Koh, who now works at Ajou University in South Korea. “This system requires only basic, passive electronic components on the robot to deliver an electric current – the structure of the robot itself takes care of the rest.”

Their creation is a new thin, plastic robot shaped like tetrahedrons. A small circuit is attached to the central triangle, and the outer three triangles are connected with hinges.

Coils made from a type of metal called shape-memory alloys are attached to the hinges; these can be deformed then recover their original shapes after heating. When the robot is in its flat “unfolded” state, the coils are stretched. Inducing an electric current in the circuit using wireless electromagnetic power transmission (the same technology used in wireless charging pads) causes the coils to heat up and contract to their original shape. This causes the outer triangles to fold towards the centre.

When the current stops, the coils are stretched back to their original shape due to the stiffness of the hinges. This unfolds the robot once again. Adding a resonator to each coil which responds to only specific electromagnetic frequencies can cause each coil to contract independently.

To demonstrate the capabilities of the origami-inspired design, the researchers built a small robotic arm capable of bending to the left and right, and opening and closing a gripper using coils tuned to different frequencies.

This simple robotic technology could have numerous applications, such as in creating micro robots able to be swallowed, and unfolding within the body to perform simple tasks, or, with larger source coils, enabling wireless battery-free communication between smart objects in a home.

“Medical devices today are commonly limited by the size of the batteries that power them, whereas these remotely powered origami robots can break through that size barrier and potentially offer new, minimally invasive approaches for medicine and surgery in the future,” said Professor Donald Ingber, founding director of the Wyss Institute.