Researchers at The Massachusetts Institute of Technology (MIT), the University of Sheffield, and the Tokyo Institute of Technology have demonstrated a tiny origami robot that unfolds itself from a swallowed capsule. Steered by external magnetic fields, the bot can crawl across the stomach wall to remove a swallowed button battery or patch a wound.

The robot propels itself using “stick-slip” motion, in which appendages stick to a surface through friction when it executes a move, but slip free again when the body flexes to change its weight distribution.

A pattern of slits in the robot's outer layers determines how the origami-inspired device will fold when its middle layer contracts. To enable compression to the size of a capsule, the researchers arrived at a rectangular design with accordion folds perpendicular to the robot's long axis. Additionally, pinched corners act as points of traction.

In the center of one of the forward accordion folds is a permanent magnet that responds to changing magnetic fields outside the body, which control motion. Applied forces applied are principally rotational. A quick rotation will make the robot spin in place, but a slower rotation will cause the device to pivot around one of its fixed feet.