Researchers at the Massachusetts Institute of Technology, England’s University of Sheffield, and the Tokyo Institute of Technology have developed a life-saving tiny origami robot that can unfold itself from a swallowed capsule to complete specific tasks within the human body. Steered by external magnetic fields, in its first demonstration the tiny bot was encased in an ice capsule and then introduced, as if swallowed, into a simulation of the human esophagus and stomach. It then successfully crawled across the stomach wall to remove a swallowed button battery attached to the lining.
The research team chose to demonstrate the removal of a swallowed button battery, and the treatment of consequent wounds, because they felt it was a compelling application of their origami robot. Every year, 3,500 swallowed button batteries are reported in the U.S. alone. The batteries are sometimes digested normally, but if they come into prolonged contact with the lining of the esophagus or stomach, they can cause an electric current that produces hydroxide, causing painful burning of the tissue.
In order to make the robot ingestible, the team of researchers experimented with various possible solutions until they finally came up with the accordion-pleated design, which is compressible enough to fit into a capsule. They then encase this in an ice capsule, which melts when it reaches the stomach, allowing the robot to unfold like origami, into its fully functional rectangular shape.
A permanent magnet is located in the center of one of the forward accordion folds. This magnet responds to changing magnetic fields outside the body, which then control the robot’s motion. The robot responds to rotational forces. A quick rotation makes it spin in place, but a slower rotation will cause it to pivot around one of its fixed feet.
The researchers tested different possibilities for the structural material before choosing the same pig intestine used in sausage casings. The shrinking layer is a biodegradable shrink wrap called Biolefin. Their demonstration model is an open cross-section of the stomach and esophagus, molded from silicone rubber with a mixture of water and lemon juice simulating the acidic fluids in the stomach.
The team presented their origami robot in Stockholm, Sweden at the International Conference on Robotics and Automation in May, 2016. Their work is based on a length sequence of papers from the head of the team, Daniela Rus, who is the Andrew and Erna Viterbi Professor in MIT’s Department of Electrical Engineering and Computer Science. Rus also directs MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL).
In an interview with Larry Hardesty in MIT News, Rus said, “It’s really exciting to see our small origami robots doing something with potential important applications to health care. For applications inside the body, we need a small, controllable, untethered robot system. It’s really difficult to control and place a robot inside the body if the robot is attached to a tether.”
Joining Rus are Shuhei Miyashita, who was a postdoc at CSAIL when the work was done and is now a lecturer in electronics at the University of York, in England; Steven Guitron, a graduate student in mechanical engineering; Shuguang Li, a CSAIL postdoc; Kazuhiro Yoshida of Tokyo Institute of Technology, and Dana Damian of the University of Sheffield, in England.