An ingestible origami robot may one day be sent on lifesaving excavation missions to remove items, such as small batteries, from the stomachs of patients who ingest them.

The robot — which can unfold itself from a capsule and crawl across the stomach wall to retrieve items or perhaps patch a wound — was developed by researchers from Massachusetts Institute of Technology (MIT), the University of Sheffield, and the Tokyo Institute of Technology.

It moves itself using a “stick-slip” motion, where its appendages stick to a surface through friction and then slip free when its body “flexes”. The robot has two layers that surround a material that shrinks when heated, and in the outer layer, a pattern of slits determines how the robot will fold when the middle layer contracts.
“It’s really exciting to see our small origami robots doing something with potentially important applications to health care,” said Daniela Rus, the Andrew and Erna Viterbi professor of MIT’s Department of Electrical Engineering and Computer Science, in a statement.

This new robot is based on Rus’ previous papers on origami robots, and is different from previous robots in that the new design is based on a biocompatible material, Biolefin.

It had to be small enough to fit inside a capsule, according to the announcement, and when the capsule dissolved, the forces acting on the robot had to be strong enough to cause it to unfold. The team created a rectangular robot with accordion folds and one of the folds holds a magnet. Magnetic fields outside of the body controlled the robot’s motions.

In the following video, Rus explains that the robot can remove foreign objects, patch wounds or possibly even deliver medicine at designated locations.



For the researcher’s experiments, the robot used the magnet to pick up the button battery.

The stomach that the team designed was molded from a silicone rubber with the same mechanical properties as a pig, and water and lemon juice simulated the acid found in the stomach. Also, the structural material of the robot was dried pig intestine used in sausage casings.

Every year, 3,500 button batteries are reportedly swallowed in the U.S. alone, according to the announcement, and frequently will be digested. However, if they come into prolonged contact with the esophagus or stomach tissue, they can cause an electric current that produces hydroxide, burning the tissue.

“[First author, Shuhei Miyashita] bought a piece of ham, and he put the battery on the ham,” Rus said. “Within half an hour, the battery was fully submerged in the ham. So that made me realize that this is important.”

“This concept is both highly creative and highly practical,” said Bradley Nelson, a professor of robotics at the Swiss Federal Institute of Technology, in a statement. “It addresses a clinical need in an elegant way.”

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