A team of Scientists at MIT and Brigham and Women’s Hospital have developed a flexible sensor that can be rolled up and swallowed. After it is ingested, the sensor sticks to the intestinal lining or the stomach wall, where it can measure the digestive tract’s rhythmic contractions.
Such sensors could help Doctors to diagnose gastrointestinal disorders that slow down the passage of food through the digestive tract. They could also be used to detect food pressing on the stomach, helping Doctors to monitor food consumption by patients being treated for obesity.
The flexible devices are based on piezoelectric materials, which produce a current and voltage when they are mechanically deformed. They also integrate polymers with elasticity similar to that of human skin, so that they can adapt to the skin and stretch when the skin stretches.
In a paper published in the October 10th issue of Nature Biomedical Engineering, the team demonstrated that the sensor stays active in the stomachs of pigs for up to two days. The device’s flexibility could offer better safety over more rigid ingestible devices, the Researchers say.
“Having flexibility has the potential to impart significantly improved safety, simply because it makes it easier to transit through the GI tract,” says Giovanni Traverso, a Research Affiliate at MIT’s Koch Institute for Integrative Cancer Research, a Gastroenterologist and Biomedical Engineer at Brigham and Women’s Hospital, and one of the senior Authors of the paper.
Canan Dagdeviren, an Assistant Professor in MIT’s Media Lab and the Director of the Conformable Decoders research group, is the paper’s Lead Author and one of the Corresponding Authors. Robert Langer, the David H. Koch Institute Professor and a member of the Koch Institute, is also an Author of the paper.
Flex those sensors
Traverso and colleagues have earlier built ingestible devices that can be used to deliver drugs to the digestive tract or monitor vital signs. With the goal of creating a more flexible sensor that might offer better safety, Traverso partnered with Dagdeviren, who had earlier developed flexible electronic devices such as flexible mechanical energy harvesters and a wearable blood pressure sensor.
To produce the new sensor, Dagdeviren fabricates electronic circuits on a silicon wafer as a first step. The circuits have two electrodes: a gold electrode positioned atop a piezoelectric material known as PZT, and a platinum electrode on the underside of the PZT. After the circuit is fabricated, it can be removed from the silicon wafer and printed onto a flexible polymer called polyimide.
The ingestible sensor that the Researchers engineered for this research is 2 by 2.5 cm and can be rolled up and placed in a capsule that dissolves after being ingested.
In tests in pigs, the sensors effectively adhered to the stomach lining after being implanted endoscopically. Through external cables, the sensors conveyed information regarding how much voltage the piezoelectrical sensor produced, from which the Researchers distinguish when food or liquid was ingested as well as could calculate how much the stomach wall was moving.
For the first time, we showed that a flexible, piezoelectric device can stay in the stomach up to two days without any electrical or mechanical degradation.
Canan Dagdeviren, Assistant Professor, Media Lab, MIT and the Director of the Conformable Decoders research group
This type of sensor could make it easier to diagnose digestive disorders that impair motility of the digestive tract, which can result in trouble swallowing, gas, nausea or constipation.
It could also be used by doctors to help measure the food consumption of patients being treated for obesity.
Having a window into what an individual is actually ingesting at home is helpful, because sometimes it’s difficult for patients to really benchmark themselves and know how much is being consumed.
Giovanni Traverso, Research Affiliate, Koch Institute for Integrative Cancer Research, MIT
In future versions of the device, the Researchers plan to harvest some of the energy produced by the piezoelectric material to power other features, including more wireless transmitters and sensors. Such devices would not need a battery, additionally improving their potential safety.
The research was funded partly by a postdoctoral fellowship from the Swiss National Foundation, the National Institutes of Health, the Max Planck Research Award, the Alexander von Humboldt-Stiftung Foundation, and the Division of Gastroenterology at Brigham and Women’s Hospital.