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TECH FRONT E


Ingestible Origami Robot Unfolds to Rescue Swallowed Objects


very year 3500 swallowed button batteries are reported in the US alone. Fortunately, the batteries are often digested normally. However, prolonged contact with the esophagus or stomach can cause an electric current that produces hydroxide, which burns the tissue. In experiments involving a simulation of the human esophagus and stomach, researchers at MIT, the Univer- sity of Sheffi eld, and the Tokyo Institute of Technology have developed a tiny origami robot that can unfold itself from a swallowed capsule and crawl across the stomach wall to retrieve a swallowed button battery or patch a wound. “For applications inside the body, we need a small,


controllable, untethered robot system,” said Daniela Rus, one of the researchers and the director of MIT’s Computer Science and Artifi cial Intelligence Laboratory (CSAIL). “It’s really diffi cult to control and place a robot inside the body if the robot is attached to a tether.” The robot can propel itself using


what’s called a “stick-slip” motion, in which its appendages stick to a sur- face through friction when it executes a move, but slip free again when its body fl exes to change its weight distri- bution. The robot consists of two lay- ers of structural material sandwiching a material that shrinks when heated. A pattern of slits in the outer layers de- termines how the robot will fold when the middle layer contracts. Researchers were confronted with additional design challenges: the robot needed to be compressed so that it was small enough to fi t inside a capsule and it needed to be strong enough to fully unfold once the cap- sule was swallowed and dissolved. As a result, the robot is rectangular with accordion folds perpendicular to its long axis and pinched corners that act as points of traction. The robot is also equipped with a permanent magnet that responds to changing magnetic fi elds outside the


July 2016 | AdvancedManufacturing.org 37


An example of a capsule and the unfolded origami device.


body, which control the robot’s motion. The forces applied to the robot are principally rotational. A quick rotation will make it spin in place, but a slow rotation will cause it to pivot around one of its fi xed feet. In trials, the robot also used the same magnet to retrieve a button battery.


Photo courtesy of MIT


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