Deadly intestinal cancers are on the rise, and the best chance to beat them is with an early diagnosis. But current techniques used to inspect the digestive tract are highly invasive, scaring many patients away. Some researchers hope that soft, magnetically controlled robots the size of a vitamin capsule could replace these diagnostic methods in a few short years.

A team led by Qingsong Xu, a professor of electromechanical engineering at the University of Macau in China, recently unveiled a micro-robot prototype inspired by the locomotion of an African spider that cartwheels across the desert dunes of Namibia instead of crawling.

The robot, made of a rubber-like magnetic material, has been tested in animal stomachs, colons, and small intestines. The researchers said it successfully navigated the “complex environment” of the digestive tract, full of mucus, sharp turns, and obstacles as tall as 8 centimeters high. ****

****Today’s procedures use endoscopes, flexible tubes fitted with a camera that doctors insert into the patient’s digestive tracts through the mouth or rectum. ****The procedure requires sedation due to the extreme discomfort it causes to the patient, and improper manipulation with the endoscope can cause serious injuries, including bowel perforation. Some patients might delay the investigation out of fear, which could have catastrophic consequences as cancer might spread. Other diseases, such as stomach ulcers and Crohn’s disease are also diagnosed with endoscopy.

****“Traditional endoscopes cause a lot of discomfort and cannot easily access complex deeper regions inside the body,” Xu told IEEE Spectrum. “The purpose of the soft magnetic robot is to provide a minimally invasive, controllable, and highly flexible alternative.”

How the Robot Moves

Soft magnetic robots, like that developed by Xu, offer a more palatable alternative to endoscopy. The robot, the size of a large vitamin capsule, could be swallowed with relative ease and pass through the stomach and the entire length of the small and large intestines, propelled by an externally applied magnetic field. The robotic mini-spider could perform detailed inspections of the complicated terrain without bothering the patient too much. At the end of its journey, it passes out of the body just like processed food.

Other teams have experimented with various types of robot locomotion, including crawling, jumping, and swimming, the researchers said in a paper describing the new robot, published in the International Journal of Extreme Manufacturing last month. Those earlier designs, however, had limitations when traversing such complex environments as the digestive tract.

These series of images show how the robot moves through the stomach. In the rightmost column, the researchers also demonstrate targeted drug delivery. Ruomeng Xu, Xianli Wang, et al.

“We went for a design inspired by the golden wheel spider, because it provided superior obstacle crossing ability and energy efficiency compared to other locomotion models,” Xu said. “By mimicking this type of locomotion in the patient, the robot can navigate in the mucus, in the folded and even vertically inclined surfaces with remarkable stability.”

The golden wheel spider is a small arachnid, about 2 centimeters wide, that escapes danger by curling its legs around its body and rolling down the sloping desert dunes. The robot developed by the Macau team uses the same strategy, but instead of being propelled by gravity, it rolls through the digestive tract thanks to an external magnetic force that interacts with tiny magnets in the robot’s legs. To control the robot with precision, the researchers created a dexterous robotic arm fitted with a powerful rotating magnet that sits next to the patient during the procedure.

The Future of Gut Diagnostics

The researchers plan to perform further experiments with live animals and, if all goes well, move to clinical trials with humans. Xu hopes the soft spider robots could help doctors examine patients’ insides in as little as five years.

“The medical community increasingly recognizes the potential of soft magnetic robots to revolutionize endoscopic procedures by minimizing patient discomfort and increasing precision,” said Xu. “There is a lot of interest in the medical world.”

In the not-so-distant future, advances in micro-robotics may enable targeted drug delivery in the treatment of ulcers or tumors. The tiny robots could also be used in a range of minimally invasive interventions and examinations. The field has been growing rapidly in the past few years, although no such robots have yet made it into clinical practice, and magnetically controlled robots are a promising field of development many researchers are exploring.

For example, a team from North Carolina State University recently presented another such robot, also using a flexible magnetic material. Instead of cartwheeling, the North Carolina robot crawls through the digestive tract like a caterpillar; the external magnetic forces induce contractions in its 3D-printed origami-style structure. A paper published in the journal Advanced Functional Materials described experiments with the robot delivering mock treatment to a mock stomach ulcer.

Xiaomeng Fang, assistant professor in material engineering at North Carolina State University and lead author of the paper, told IEEE Spectrum the work has garnered a lot of interest. “These robots are soft and they can be controlled remotely,” she said. “They can also change their shape, which makes them very interesting for treatment of internal diseases.”