Origami Robot In Ingestible Capsule Removes Battery Inside Simulated Stomach

A new work which will be presented at the International Conference on Robotics and Automation this week builds on a long order of papers on origami robots from the research group of Daniela Rus, the Andrew and Erna Viterbi Professor in MIT's Department of Electrical Engineering and Computer Science.

Researchers at the Massachusetts Institute of Technology (MIT), the University of Sheffield, and the Tokyo Institute of Technology have conducted experiments that involved a simulation of the human esophagus and stomach. The tiny origami robot can unfold itself from a swallowed capsule and guided by external magnetic fields, crawls across the stomach wall to remove a swallowed button battery or cover a wound, Science Daily reported.

"It's really exciting to see our small origami robots doing something with potential important applications to health care," says Rus, who also directs MIT's Computer Science and Artificial Intelligence Laboratory (CSAIL). "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."

With Rus on the paper are first author 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, who was visiting MIT on sabbatical when the work was done; and Dana Damian of the University of Sheffield, in England.

According to MIT News, though it is said that the new robot is a successor of one which was submitted at the same conference last year, the body design of the new robot is significantly different. Like its predecessor, it can propel itself using what's called a "stick-slip" motion, in which its appendages stick to a surface through friction when it executes a move, but slip free again when its body flexes to change its weight distribution.

A host of structural modification was inspired by how the robot was envisioned. "Stick-slip only works when, one, the robot is small enough and, two, the robot is stiff enough," says Guitron. "With the original Mylar design, it was much stiffer than the new design, which is based on a biocompatible material." To make up for the biocompatible material's relative malleability, the researchers had to think of a design that required fewer stilts. However, the robot's folds increase its stiffness along certain axes.

But because the stomach is filled with fluids, the robot doesn't rely entirely on stick-slip motion. "In our calculation, 20 percent of forward motion is by propelling water - thrust - and 80 percent is by stick-slip motion," says Miyashita. "In this regard, we actively introduced and applied the concept and characteristics of the fin to the body design, which you can see in the relatively flat design."

The robot should also be easy to compress so it could fit inside a capsule to be swallowed, at the same time, the forces acting on it should be strong enough to cause it to fully unfold when the capsule dissolves. Through a design process that Guitron describes as "mostly trial and error," the researchers arrived at a rectangular robot with accordion folds perpendicular to its long axis and pinched corners that act as points of traction.