The robot unfolds from an ingestible capsule where it can then go on to carry out specific tasks, such as; remove foreign objects, repair wounds and deliver medicine at designated locations – eliminating the need for surgery.
It was decided, after a number of tests, that the best biocompatible material to use would be dried pig intestine, used in sausage casings. The robot is then placed in to a capsule of ice which melts in the stomach and allows the robot to fold out into its functional form. An external magnetic field is then used to control the robot.
Involved in the project are researchers from MIT, Dr Dana Damian from theDepartment of Automatic Control and Systems Engineering at the University of Sheffield, and researchers from the Tokyo Institute of Technology. The team have carried out experiments involving a simulation of the human oesophagus and stomach and have demonstrated a tiny origami robot that can unfold itself from a swallowed capsule and, steered by external magnetic fields, crawl across the stomach wall to remove a swallowed button battery, for example or patch a wound.
Their work which will be presented at this week’s International Conference on Robotics Automation builds on a long sequence of research 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.
“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.”
The challenge for the team of researchers was finding biocompatible materials that are easy to be controlled and amenable to the types of operations that are needed from the robot. The chosen biocompatible material (dried pig intestine) is naturally a more malleable material than the material used in previous versions, so adaptations had to be made to create a stiffer structure.
The robot consists of 2 layers of structural material, sandwiching a material that shrinks when heated and a pattern of slits in the outer layers determines how the robot will fold when the middle layer contracts. The robot not only has to be stiff enough but also small enough to propel itself, something which is called ‘stick-slip’ motion, in which the robots 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. To compensate for the use of a more flexible material the team had to come up with a design which had fewer slits, but still allowed the robot to fold in to the correct size.
In the centre of one of the front folds the researchers put in a magnet that responds to changing magnetic fields outside the body and controls the robots movement. A variation in applied magnetic forces instruct the robot where is should go and what it should do.
Every year, 3,500 swallowed button batteries are reported in the U.S. alone. Frequently, the batteries are digested normally, but if they come into prolonged contact with the tissue of the oesophagus or stomach, they can cause an electric current that produces hydroxide, which burns the tissue. The origami robot can be used for instances such as this, locating the battery in the stomach, lifting the lodged battery out of the stomach coating and then eliminate it out of the digestive systems – removing the need for surgery.
We are moving toward medical technology that is less invasive and more autonomous and thus can provide safe, improved and consistent outcomes. This work is among the first examples and shows the first transformable in-stomach robot that can perform multiple repair tasks.
DR DANA DAMIAN
You can find out more about the Ingestible Origami Robot and future advances by watching the following video: