MIT-Led Team Unveils Edible, Magnetically Controlled Origami Robot for Gastric Foreign Body Removal

Recently, researchers from MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL), the University of Sheffield, and the Tokyo Institute of Technology jointly developed a folding robot made from pig large intestine. Controlled by external magnetic forces, the folding robot can move through simulated human esophagus and stomach environments, enabling applications such as removing accidentally ingested button batteries, repairing wounds, and targeted drug delivery.

The origami robot showcased at this month’s International Conference on Robotics and Automation was developed based on a series of origami robots created under the leadership of CSAIL Director Daniela Rus and MIT Professor of Electrical Engineering and Computer Science Andrew and Erna Viterbi.

Rus stated, “It is truly exciting to see that our foldable robots can perform tasks with potential benefits for healthcare. For applications involving entry into the human body, we require robotic systems that are small, controllable, and free from tethered traction. If a robot needs to be tethered by a cable, it becomes extremely difficult to operate and control.”

Team Composition

The team that co-developed the foldable robot with Rus included Shuhei Miyashita, a postdoctoral associate at the MIT Computer Science and Artificial Intelligence Laboratory (CSAIL) and a lecturer in electronics at the University of York, UK; graduate student in mechanical engineering Steven Guitron; Shuguang Li, a postdoctoral associate at the MIT CSAIL; Kazuhiro Yoshida from the Tokyo Institute of Technology, who was visiting MIT at the time; and Dana Damian from the University of Sheffield, UK.

Upgraded Version of the Previous Folding Robot

This new robot is an upgraded version of the one showcased at last year’s International Conference on Robotics and Automation, featuring significant design differences. It achieves self-propulsion through “stick-slip motion,” where appendages adhere to object surfaces via friction; when the folded robot bends, it alters its center of gravity distribution, thereby enabling free sliding.

Like the series of origami robots previously designed by Rus’s team, the new robot consists of two layers of structural materials. The material in the middle layer shrinks when heated, while the gap structure of the outer layer determines how the robot folds as the middle layer begins to contract.

Expectations for the robot also highlight the structural adjustments of this foldable robot. Guitron explained that there are two conditions for the successful operation of "stick-slip motion": first, the robot must be small enough, and second, it must be strong enough. The robot in question is made of biocompatible materials, so it will not cause rejection.

Because the stomach is filled with fluid, the robot does not rely entirely on stick-slip locomotion. “According to our calculations, 20% of the forward propulsion comes from the water, and 80% comes from stick-slip motion,” said Miyashita.

The robot must be compressed to a sufficiently small size to be encapsulated and ingested. Similarly, once the capsule dissolves, the forces acting on the robot must be strong enough to allow the folded robot to fully unfold. After numerous trials, this rectangular robot, which can be folded like an accordion, was finally developed.

A permanent magnet is embedded in the middle section of the foldable structure. The magnet responds to external stimuli, enabling users to control the folding robot. The robot utilizes the same magnetic force to attract button-cell batteries.

Materials

Researchers previously experimented with more than 20 different materials to construct the robot’s framework. After spending considerable time sourcing materials in the Asian market and Chinatown, they ultimately selected air-dried pig intestines—commonly used for sausage casings—with a layer of biodegradable shrink film, Biolefin, sandwiched in between.

This simulated cross-section of an artificial esophagus and stomach is made of silicone rubber, using a mixture of water and lemon juice to simulate gastric acid.

Can be used to remove foreign bodies from the stomach

According to reports, there are 3,500 cases of button battery ingestion annually in the United States alone. Typically, batteries can be passed through the digestive system without issue. However, if they remain in prolonged contact with esophageal or gastric tissue, they can generate an electric current that produces hydroxide ions, causing chemical burns to the tissue.

Miyashita employed a clever method to demonstrate to Rus the critical importance of promptly removing ingested button batteries. Miyashita purchased a slice of ham and placed a button battery on it; within less than half an hour, the battery had become completely embedded in the ham. Therefore, if a battery is truly lodged in the human body, it must be removed as soon as possible.

Professor Bradley Nelson of ETH Zurich stated, “This concept is both creative and feasible, offering an elegant solution to this medical consultation challenge. It is the most compelling origami robot I have ever seen.”

Rus stated that the foldable robots would be further improved by adding sensor capabilities, enabling them to autonomously control their operations without relying on external magnetic fields.