Snake-Inspired Soft Robot Crawls Deep Into the Small Intestine

How does a robot slither?

A snake steers by contracting muscles on one side of its body, then the other. The MIT team copied that trick with multifunctional actuators — soft devices that drive the robot's motion. Each actuator contains four chambers, and inflating them in different combinations makes the tube extend or bend in any direction.

"By tuning the amount of air that goes into these chambers, you can tune the direction that the robot is moving in," Traverso explains.

The head and tail segments carry expandable anchoring balloons that take turns inflating and deflating, pulling the robot forward. And here's the clever part: those segments wear patterned sleeves inspired by kirigami, the Japanese paper craft that cuts as well as folds. The sleeves lie flat until the balloon stretches them, at which point tiny three-dimensional needles pop out. Like snake scales, these needles grip the intestine's slippery mucosal lining.

That grip matters. "By using kirigami sleeves to enhance surface friction, the robot can generate localized tissue engagement traction for locomotion without relying on excessive stretching of the delicate small intestinal tissue," says Ahmad Mujtaba Jebran, an MIT graduate student and one of the paper's lead authors.

The other lead authors are Binbin Ying, a former MIT postdoc now at University of Texas Southwestern Medical Center, and Sahab Babaee, a former MIT research scientist. Traverso's lab has used the same kirigami approach before, in traction-boosting shoe sole coatings and in esophageal stents that temporarily lodge in place and release drugs.

What does this change for patients?

Right now, not much — and that caveat deserves emphasis. The tethered robot, which enters through the mouth or rectum and connects by cable to external controllers, has been tested only in animals. In those studies, it demonstrated a camera for imaging, a sprayer for drug delivery, and clips that can take tissue biopsies or remove polyps, all guided by a human-operated controller.

A six-and-a-half-foot crawl is also well short of the full 20-to-25-foot organ. The team says it is now improving the navigation systems and testing additional applications in the small intestine.

"We hope we can continue to move it forward to eventually develop systems that can help achieve more automated evaluation of the small intestine," Traverso says.

Eventually. That word is doing real work here. Before any human patient benefits, the robot needs better navigation, longer range and clinical trials. Still, if the approach holds up, a procedure that today demands painstaking manual balloon-pumping could one day become semi-automated — faster, easier to control, and able to diagnose and treat in a single pass.

The research drew funding from a long list of sources, including the Karl van Tassel Career Development Professorship, the MIT Department of Mechanical Engineering, Banting and NSERC postdoctoral fellowships, the UT Southwestern Medical Center Startup Fund, Samsung Semiconductor and Eurnekian Nanotechnology Graduate Student Fellowships, the Cooke Undergraduate Transfer Scholarship, and MIT's Undergraduate Research Opportunities Program.