Using materials that are safe for human consumption, MIT researchers have created tiny batteries that could be used to power ingestible electronic devices. The entire battery is bioresorbable, meaning that it can be fully broken down and absorbed by the body. Credit: Courtesy of the researchers; MIT News
Using materials safe for human consumption, MIT researchers have created tiny batteries that could be used to power ingestible electronic devices.
Giovanni Traverso, a professor of mechanical engineering at MIT, and his team have been developing ingestible capsules for over a decade. Not all of these devices require a power source. For those that do, the researchers have powered the devices from an external source that wirelessly transmits power, harvested power from the GI tract, or used small coin batteries. However, those batteries, which usually contain lithium, silver oxide, or other metals, could pose a safety risk if the battery’s protective coating was damaged while traveling through the GI tract.
To create a safer battery and allow the systems to be fully self-contained with no external power needed, the researchers turned to metals that can act as electrodes but are safe for human consumption in small amounts— agnesium and molybdenum trioxide.
“For many of the systems we’re developing, we need power, and we power the system through different ways,” said Traverso. “Often, we use batteries, so the question here was: Could we develop a battery that was bioresorbable, and then apply that across a range of application areas?”
Biocompatible batteries
In the new study, published in Nature Chemical Engineering, researchers used magnesium to build the battery's anode and molybdenum trioxide for its cathode, paired with an ionic liquid gel electrolyte, making the entire system bioresorbable.
They built two versions for different applications: a 7.5-millimeter disc and a 24-millimeter rectangular bar. Tested in a highly acidic solution similar to gastric juice, the batteries functioned normally for about three days before performance began to decline, breaking down completely within a few weeks.
The researchers then incorporated the rectangular battery into a degradable device they first reported in 2023, which is designed to deliver a small electrical current to the lining of the stomach. In their earlier work, Traverso’s lab showed that this jolt could stimulate endocrine cells in the stomach to produce ghrelin— a mechanism that could help treat conditions involving nausea or appetite loss.
The original version of the device ran on two silver oxide coin batteries. Swapping in the new magnesium-molybdenum oxide batteries made nearly the entire device bioresorbable. In the new study, the battery generated continuous stimulation for up to three days, and in animal tests, 20 minutes of stimulation boosted ghrelin levels by about 50%.
“What makes this work exciting is that we were able to show that a bioresorbable battery is not just a concept,” said lead author Mehmet Girayhan Say, former MIT postdoc. “It can actually power clinically relevant functions inside the gastrointestinal tract and then simply dissolve.”
Battery-powered communication
The team also built the disc-shaped battery into an RFID capsule designed to help patients stick to their medication schedules by transmitting its location from within the GI tract.
An earlier version of the system relied on passive RFID tags powered by harvested energy, which limited its transmission range. With the new battery, animal tests showed the device could transmit continuously and over a longer range, up to 1.5 meters.
The researchers are now planning a clinical trial of the system, expected to begin in about two years.
Such systems could not only be safer for patients, but also would reduce the environmental impact of batteries that would eventually be excreted into the sewage system.
“The benefits are twofold: one, the ability to be bioresorbable, but also the potential to minimize environmental impact because the materials will be degraded in the environment as well,” said Traverso.