A pill that unfolds into a little robot could one day give parents everywhere a little more peace of mind. Once swallowed, it can open up inside a person's stomach, crawling across the stomach wall to retrieve a single-cell button battery, and even patch wounds.
This is no small thing. In the US every year, over 3,500 incidents of swallowed button batteries are reported in the US, and most cases of battery swallowing involve toddlers. Although most of these batteries are safely digested, sometimes they can leak and cause tissue burns, bleeding, and death.
Developed by an international team of researchers from MIT, the University of Sheffield in the UK and the Tokyo Institute of Technology in Japan, the origami robot is the latest developed by MIT Computer Science and Artificial Intelligence Laboratory director Daniela Rus, who has been building and researching origami robots for years.
An ingestible robot, however, poses some significant challenges.
"For applications inside the body, we need a small, controllable, untethered robot system," Rus explained in a statement. "It's really difficult to control and place a robot inside the body if the robot is attached to a tether."
The robot has a magnet attached, and its movements are controlled using magnetic fields that are applied externally. It's constructed of two layers of structural material that maintain the robot's shape, sandwiching a layer of material made from dried pig intestine (the kind used in sausage casings) that shrinks when heat is applied. Slits in the two outer layers allow the robot to fold like a small concertina when the inner material contracts.
This allows it to move along a surface a little like an inch worm. It uses what the team calls a "stick-slip" motion, whereby its pointed corners, designed for traction, will stick to surfaces using friction when it moves, but then slip free when the robot flexes.
And, because stomachs contain liquid, the robot can swim, too.
"In our calculation, 20 percent of forward motion is by propelling water -- thrust -- and 80 percent is by stick-slip motion," said first author Shuhei Miyashita, formerly a postdoc at CSAIL, now a lecturer in electronics at the University of York in the UK.
The team built a synthetic stomach out of silicone rubber, modelled on the mechanical properties of a pig's stomach, and filled it with a mixture of water and lemon juice to simulate stomach fluids. When deployed in this environment in a capsule made of ice that melts in the warm environment, the robot made its way to a button battery and picked it up using its attached magnet.
"It's really exciting to see our small origami robots doing something with potential important applications to health care," Rus said.
The team will be presenting their research at the IEEE International Conference on Robotics and Automation in Stockholm, Sweden that runs from May 16-21.