Researchers have engineered a swallowable battery crafted from paper-like materials that can energize internal medical devices before safely dissolving in the body. While initial trials have been conducted on pigs, the technology holds promise for powering temporary ingestible devices in humans, potentially eliminating the need for surgical retrieval of conventional power sources.
The study, published on Monday (Sept. 21) in Nature Chemical Engineering, details a device composed of layers including a magnesium alloy anode, a cathode containing molybdenum trioxide and activated carbon, and a biodegradable electrolyte. To manage the rate of decomposition, the team coated the battery in beeswax, with some iterations featuring an additional layer of candelilla wax derived from a desert shrub. This coating serves as a critical design element to control the battery’s functional lifespan within the acidic environment of the gastrointestinal tract.
The research team, which included Giovanni Traverso of MIT, created two battery versions. One was miniature enough to fit inside a standard gelatin capsule, producing approximately 1.77 volts, while a larger variant generated about 1.84 volts. In lab settings, the smaller unit stored 2 milliampere-hours per square centimeter, sufficient for low-power electronics.
During in vivo testing, the batteries were administered to pigs via an endoscope within 3D-printed capsules. Both prototypes operated reliably for up to three days as they traveled through the digestive system, though voltage decreased as the materials degraded. John Rogers, a materials scientist at Northwestern University who was not involved in the study, noted the impressive stability of the batteries during their passage through a large animal’s GI tract.
The team demonstrated the battery’s utility by powering two distinct devices. The smaller battery activated a wireless RFID tag positioned in the esophagus, allowing researchers to detect when the pigs consumed medication via a receiver up to 5 feet away. The larger battery powered a capsule that delivered electrical stimulation to the stomach, successfully increasing levels of the hunger hormone ghrelin without causing visible tissue damage.
Despite these successes, Reza Ghodssi, a professor at the University of Maryland, pointed out that the battery’s capacity remains low and needs to increase by an order of magnitude to be more broadly promising. Additionally, while the battery and its biodegradable components broke down, the non-biodegradable circuit board from the stimulation experiment was passed naturally by the pigs. Rogers emphasized that achieving full bioresorbability for every component would eliminate the risk of internal remnants becoming lodged in the tract.
Future work focuses on standardizing manufacturing to reduce variability caused by construction factors such as layer contact and electrolyte distribution. The researchers aim to refine the wax coatings to allow for precise control over operational timeframes ranging from hours to days. According to Traverso, longer tests mimicking human digestion are underway, with initial clinical trials for the RFID system potentially beginning in approximately two years.
Beeswax coating to control the lifespan is such a clever simple solution. Science keeps surprising me with elegant designs like this.
I’m still skeptical about passing non-biodegradable circuit boards naturally. What if it gets stuck somewhere? Safety first, always.
Wait, they increased hunger hormones on pigs? Is this going to be used for diet aids eventually? That seems like a slippery slope.
Only powers devices for three days? I worry that’s too short for most real-world medical treatments. Need better capacity.
This is incredibly exciting! No more surgery to remove implanted batteries sounds like a dream come true for patients everywhere.