Ingestible robots could help save kids who swallow batteries

Two-year-old Briana Florer loved Frozen and Minnie Mouse. She was just beginning to talk. But three days after Christmas she died after swallowing a silver button battery, Good Housekeeping reported. Her doctors believed the battery ate through her esophagus and carotid artery.

Every year, more than 3,500 people in the United States swallow button batteries. Between 2005 and 2014, doctors reported 11,940 cases of children under the age of 6 who ingested a battery.

Swallowed batteries don’t cause harm if they are digested normally. But if they become lodged in the tissue of the stomach or esophagus, they can cause an electric current that produces hydroxide, a chemical that burns and damages tissue. Chemical burns can happen within as little as two hours of battery ingestion, and surgeons often can’t remove a battery quickly enough to prevent harm.

But now researchers at MIT have developed a tiny origami robot that can unfold itself from a swallowed capsule, crawl across the stomach wall, and remove an embedded button battery or patch a wound, making surgery unnecessary.

The researchers made the rectangular robot by sandwiching a piece of Biolefin, a biodegradable material that shrinks when heated, between two layers of dried pig intestine like that used in sausage casings.

“We spent a lot of time at Asian markets and the Chinatown market looking for materials,” researcher Shuguang Li said.

The scientists made slits in the two outer layers to allow the robot to bend and move when the middle layer contracts. Then they folded the robot accordion-style, pinched the corners to provide points of traction, and placed a permanent magnet in the center of one of the front folds, allowing doctors to control the robot with magnetic fields outside the body.

Next the scientists compressed the robot so it would fit into a capsule small enough to swallow. The researchers tested the mechanical properties of a pig stomach and then made an open cross-section silicone model of the stomach and esophagus. They used a mixture of water and lemon juice to simulate acidic stomach fluids.

The robot unfolded itself when the capsule dissolved in the fluids and then propelled itself through a combination of liquid propulsion and “stick-slip” motion in which its appendages stick to a surface because of friction and then slip free when its body flexes. The robot eventually used its permanent magnet to pick up the button battery.

To demonstrate the importance of retrieving an ingested battery quickly, one of the researchers put a battery on a piece of ham. Within half an hour, the battery was fully submerged in the meat.

“So that made me realize that, yes, this is important,” said Daniela Rus, one of the researchers. “If you have a battery in your body, you really want it out as soon as possible.”

The researchers say this technique can also be used to repair damaged tissue and to deliver medicine.