Wearable health and fitness trackers have become ubiquitous, constantly gathering data such as heart rate, how the wearer exercises, and sleep quality. Their popularity has left some wondering if the technology could be taken beyond the skin’s surface into places deep within our bodies—not wearable sensors but ingestible ones.
Heeding the call, materials scientists have created a new class of edible electronics. Many of the devices are already on the market.
Christopher Bettinger is one researcher who’s rethinking how we monitor our health from the inside out. He is associate professor of materials science and biomedical engineering at Carnegie Mellon. Soon after joining the university’s faculty in 2010, he became interested in developing edible electronics, part of an emerging class of transient devices that can be swallowed. Traditionally, the devices remain intact inside the body until they are removed or passed through the digestive system. Now Bettinger has developed one that can break down in the digestive system and disintegrate inside the body.
DOWN THE HATCH
Wireless endoscopes are a first-line diagnostic tool for identifying the cause of gastrointestinal (GI) bleeding. Such electronics, which must pass all the way through the body, are great for one-time or rare use but can become problematic with regular use.
The wireless endoscope is a big pill to swallow, so to speak. At roughly 2.5 centimeters long and 1.25 cm in diameter, it has a 1 percent chance of getting lodged in the GI tract. If that happens, the patient must wait for it to pass or have it surgically removed.
It is rarely a problem when the device is used as a one-time diagnostic tool, but it becomes more serious when the device is used therapeutically and needs to be employed not annually but every day.
“Chances are, one of the devices is going to get stuck,” Bettinger says, adding that the question then becomes, “How do we make devices where…maybe they’re big, but if they do get stuck, then it’s not even a big deal?”
Inspired by the endoscopes, Bettinger started developing a digestible device by reimagining the key components: the packaging and the battery. He began by designing a battery that essentially replaces lithium with melanin. He substituted biodegradable materials, like saltwater, for other components.
WRAP IT UP
The next step was to figure out how to package the battery. Bettinger needed a packaging material that was both biodegradable and flexible. In 2012 John Rogers, a professor of materials science and engineering at Northwestern University, in Evanston, Ill., discovered that silicone is ingestible and dissolves slowly in saliva and other body fluids. He found that by adjusting the silicone’s thickness, he could adjust the rate of decomposition. That meant he could program materials made of silicone to be active for set periods of time within the body, like a dissolving suture that is necessary only until a wound heals.
It was precisely the kind of material Bettinger was looking for to encase his battery. But Rogers has used silicone only for devices that are implanted in the body—not swallowed. Bettinger’s initial tests suggest the battery should work well.
The first version he developed, in 2013, remained operational for five hours, and subsequent versions lasted three times that long. He has not tested the battery in a human body, but he says he hopes to within the next few years.
After the battery has been tested and approved, Bettinger says, he hopes it could be used to power any device a clinician might want to employ, including a camera.
“Since it’s biodegradable, it’s not as risky to use them as much as every single day or every other day,” he says.
And unlike transient materials that are surgically implanted in the body, edibles are given a certain degree of latitude. “Your lunch or breakfast was probably not inspected in a factory, or sterilized, or hermetically sealed,” like an implantable device would be, Bettinger says. As long as you can ingest the materials that compose the device, the timeline for U.S. Food and Drug Administration approval is greatly reduced, from 10 or more years for testing to just a few, he says. Faster approvals leave more time for innovation—which makes room for creativity.