A Fitbit for the Stomach

Researchers Canan Dagdeviren and Giovanni Traverso demonstrate their flexible, ingestible device by placing it in their mouths and posing for a photo in a lab.
Photo: Massachusetts Institute of Technology
Canan Dagdeviren (left) of MIT and Giovanni Traverso of Brigham and Women’s Hospital pose with their flexible, ingestible sensor.

We admit to a weird fascination with electronics that can be swallowed. Whether its robots, cameras, or edible actuators, we find them James Bond-level cool.

So here’s another one for you: A flexible sensor developed at MIT and Brigham and Women’s Hospital in Boston can monitor movements in the stomach, sense ingestion, and power itself for at least two days without degrading. The device, described this week in the journal Nature Biomedical Engineering, could be used to record how frequently a person is eating and help monitor various gut disorders.

“Understanding gut movement helps us, as healthcare providers, to potentially intervene to really help patients,” says study author Giovanni Traverso, a gastroenterologist and biomedical engineer at Brigham and Women’s Hospital and Harvard Medical School.

The 2-by-2.5-centimeter device consists of a flexible polymer, called polyimide, printed with electronic circuits: A gold electrode atop a material called PZT and a platinum electrode on the underside. PZT is a piezoelectric material, capable of producing an electric charge in response to mechanical force.

The thin device can be rolled up into a capsule and swallowed, although no one was actually doing that in the current study. The engineers tested their device in pigs, using several different techniques to get it into the animals’ stomachs. Still, flexibility is paramount, said co-author Canan Dagdeviren, an assistant professor in MIT’s Media Lab in a press release, as it “significantly” improves safety by easing the device’s passage through the GI tract.

Once in the stomach, the thin sheet sticks to the mucus lining of the stomach walls and detects any movement there. That movement varies enough that the device can distinguish among different types of materials being digested, says Traverso. Plus, it harnesses that movement for energy to power itself, generating tens of millivolts in the current study. That unique ability to self-power could be replicated to develop long-term power systems for other devices in the gut and body, without the need for an external battery, adds Traverso.

The current prototype worked for 48 hours without mechanical or electrical degradation, the team found—a feat for a flexible electronic facing the acidic environment of the stomach. In the pigs, the team ran a USB cable outside the stomach to download the recorded gut activity, but Traverso has several other projects exploring ways to collect data from the GI tract via wireless communication.

For now, the device is just a proof-of-concept, but Traverso imagines that in the future doctors could use it for patients with gut movement disorders, such as gastroparesis, a condition associated with diabetes in which the stomach does not empty properly.

And once we’re all comfortable swallowing tiny circuit boards, the device could become ubiquitous, like a Fitbit to measure food intake. While it sounds easier to simply write down everything one consumes, studies show that we’re not actually very good at that. An automatic system could improve those records, and potentially lead to greater weight loss, especially for individuals struggling with obesity.

“This could help benchmark, in an objective fashion, what is being ingested to help self-regulate,” says Traverso. “We can make it easier for the individual to recognize what is happening in an unbiased way.”

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