Across the United States, a child swallows a battery once every three hours, according to one pediatric estimate, equal to about 3,300 cases annually. Based on emergency reports, the vast majority of swallowed batteries turn out to be button cells — the squat silver disks of electrochemical energy, used in hearing aids and TV clickers. Although deaths from swallowing button cells are very rare, serious complications, like what happened in Emmett’s case, can arise when a battery is caught in a child’s throat.
Thanks to recent research spearheaded by Massachusetts Institute of Technology scientists, small robotic devices could one day be used to retrieve swallowed objects, including batteries. Though the new robot wouldn’t be able to perform major esophageal surgeries, it could, possibly, patch smaller wounds in the stomach. The only thing a patient would have to do, in theory, is swallow — a bit like gulping down a spider to catch a wayward fly.
In a proof-of-concept experiment demonstrated at the International Conference on Robotics and Automation, the small device folds into an ice capsule about the size of a gummy bear. When the ice thaws inside the body, the robot unfurls as though it were a piece of origami filmed in reverse. Once flattened, the origami robot wriggles around the stomach, controlled by human operators using an external magnetic field. This is not the first device to borrow properties from origami, now a popular source of inspiration for engineers.
“For applications inside the body, we need a small, controllable, untethered robot system,” said Daniela Rus, an electrical engineer at MIT who helped create the origami robot, in a press release. “It’s really difficult to control and place a robot inside the body if the robot is attached to a tether.”
The scientists also needed to create the robot out of safe-to-ingest parts. Sharp chips of metal and plastic were verboten, so they set their sights on food. “We spent a lot of time at Asian markets and the Chinatown market looking for materials,” MIT’s Shuguang Li said in the release. The final iteration of the origami bot is made of stiff pork casing — the same stuff you might find surrounding a hot dog or kielbasa.
Swallowing non-pharmaceutical devices has a brief but remarkable medical history. Some of the first to pounce on the idea were veterinarians, who fed magnets to cows — one such therapeutic magnet was patented in 1961 — when an animal accidentally ate a nail or other metallic item. By the early 2000s, the Food and Drug Administration had approved “gut cams,” small cameras that would allow doctors to observe patients from the inside. But the early gut cams had no way to steer, and it was possible to miss points of intestinal interest if a pill-sized camera happened to be oriented in the wrong direction as the device wormed its way through the colon.
Some scientists are experimenting with robot pills that sport legs or similar means of locomotion. Other researchers have turned to magnets, tugging a magnetized bot through the gut. But such methods aren’t a panacea, as a pair of Italian biomedical engineers argued in Scientific American in 2010. Magnetic fields can “lose power with distance, and with the irregular geometry of the intestine, sudden changes in field strength can cause the capsule to jump or can entirely sever magnetic control over the pill.”
To move, this origami bot relies on an external magnetic field in combination with what the engineers describe as stick-slip motion, a jerky push-pull against the stomach lining. Once unfolded, the robot could also use its on-board magnet to pluck a battery out of the stomach’s lining. It would then maneuver its cargo through the rest of the digestive system.
So far, the MIT researchers have tested the origami robot in a synthetic rubber stomach filled with lemon juice and water. It is unclear when such a device might be ready for humans — the next steps, according to Rus, are to add sensors to the robot and test it in living animals.