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Ingestible Robot Designed for Stomach Objects, Wounds

Unfolded robot and capsule

The unfolded origami robot with magnet, at right, folds to fit in the capsule, left. (Melanie Gonick, MIT)

13 May 2016. An engineering team at Massachusetts Institute of Technology designed a tiny robotic device for swallowing into the stomach to remove foreign objects and repair wounds. Researchers that include team members at University of Sheffield and University of York in the U.K., as well as Tokyo Institute of Technology, will describe the device next week at the IEEE International Conference on Robotics and Automation in Stockholm, Sweden.

The research group led by MIT engineering and computer science professor Daniela Rus developed the prototype device, called an origami robot since it folds into an ingestible capsule, then unfolds after it reaches its destination in the stomach. The team says the device can be used to remove button batteries, the kind used in watches, often swallowed by children. As reported in Science & Enterprise, more than 3,300 of these tiny batteries were swallowed in 2013, causing choking, tissue wounds in the esophagus, and chemical burns from electricity generated by the battery.

Rus’s lab that studies these so-called soft robots designed an earlier version of the origami robot that it presented at the same conference last year. The earlier version propels itself by first sticking to a surface then slipping free by changing its weight distribution. The new version also uses stick-and-slip propulsion, but adds a fin to take advantage of the fluid environment that would also move the device through the stomach.

The MIT team had to make other changes to accommodate the demands of an ingestible device for medical purposes. “For applications inside the body,” says Rus in a university statement, “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.”

Like the first version, the new origami robot is made with three layers of material, two outer structural layers and a middle layer that shrinks when heated. When heated the shrinking middle layer folds the device along a pattern of slits in the outer layer. To make the device small enough to be swallowed when folded, the team uses Biolefin, a flexible biocompatible material used in shrink-wrapped sausage casings, with accordion folds that the researchers say they designed after a trial-and-error process.

A tiny magnet inside the device allows the device to be guided with an external magnetic field. That same magnet attaches to the button battery to be removed from the stomach. The researchers tested the device folded into a capsule made of ice in a simulated cross-section esophagus and stomach model, made from a pig stomach, with water and lemon juice to simulate acids in the stomach. After the ice melted away, the team says it was able to rotate the external magnetic field at different speeds to make the device either spin in place or pivot on one of its feet.

The researchers believe the device can be enhanced to perform more autonomous and complex tasks, such as fix wounds in the stomach or deliver drugs. Rus tells more about the origami robot in the following video.

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