A new type of paper battery developed by Massachusetts Institute of Technology researchers can operate inside the body for a limited period before dissolving safely in the gut, offering a power source for temporary medical devices. Ingestible and implantable electronics are increasingly seen as a less invasive alternative to surgery to monitor the gut, track whether patients have taken their medications, and deliver electrical stimulation. Conventional lithium-ion and alkaline power cells, however, carry risks of leaking corrosive electrolytes, generating gas if casings fail, or leaving non-degradable electronic waste behind in the gastrointestinal tract.
To overcome these safety hazards, Giovanni Traverso and his colleagues at the Massachusetts Institute of Technology built a bioresorbable power source using materials considered safe for human consumption in small amounts, as described in research published on 21 September in Nature Chemical Engineering.
Cellulose and Molybdenum Trioxide Chemistry
The research team selected magnesium as the anode and molybdenum trioxide for the cathode, according to Mehmet Girayhan Say, a materials scientist at Chalmers University of Technology who led the study. Plant-derived cellulose fibres hold the two metal layers together. This configuration produces thinner, sturdier electrodes with better electrical contact while preserving the material’s capacity to break down naturally inside the body.
Instead of traditional water-based or buffered saline electrolytes, the team utilized a biodegradable liquid made by melting together two food-safe ingredients: choline chloride and lactic acid. This formulation yields a more stable voltage output than previous designs.
Ionic Liquids and Voltage Stability
Kourosh Kalantar-Zadeh at the University of Sydney, who was not involved in the project, notes that this performance directly supplies sufficient voltage and relatively okay energy density to drive basic integrated circuits.
To control timing within the digestive tract, the battery is encapsulated in natural waxes, using beeswax for short-term protection and a plant wax for longer retention. The technology is manufactured in two formats: a small circular cell designed to fit inside a standard capsule, and a larger version intended for more power-hungry devices.
Simulated Gastric Fluid and Safe Dissolution
When tested in simulated stomach acid, both formats degrade progressively over weeks to months. Say explains that the electrode thicknesses and cathode loading were chosen so that complete dissolution releases quantities of magnesium and molybdenum that remain below established daily tolerable intake limits.
RFID Tags and Hormone Stimulation in Animal Trials
Researchers tested two distinct devices powered by the new battery in pigs. The first application featured a radio-frequency identification (RFID) tracking tag enclosed in a swallowable gel capsule, which transmitted a wireless signal to a reader outside the body. Powered by the paper battery, the tag communicated over longer distances than typical passive tags, and its signal weakened as soon as it moved from open air into body tissue.
The second device delivered several days of continuous electrical stimulation to the stomach wall via an ingestible hormone stimulator. This intervention raised levels of the hunger hormone ghrelin without damaging surrounding tissue. The batteries remained stable in the stomach for at least three days before degrading over a period of a few weeks. Say emphasizes that the core advancement is enabling a fully bioresorbable, retrieval-free electronics platform for the gastrointestinal tract.
Materials and operational lifespan of the edible battery
What materials make up the edible battery?
The battery uses magnesium for the anode, molybdenum trioxide for the cathode, plant-derived cellulose fibres for structural integrity, and a biodegradable ionic liquid made from choline chloride and lactic acid as the electrolyte. Natural waxes like beeswax provide outer encapsulation.
How long does the battery last inside the body?
The battery can operate inside the stomach for at least three days—delivering continuous power for applications such as electrical stimulation—before breaking down progressively and dissolving completely over a period of weeks to months.
What medical applications can this technology power?
Researchers have demonstrated the battery powering a wireless RFID tracking tag and an ingestible electroceutical stimulator that regulates gut-brain hormones like ghrelin, pointing toward fully self-contained, dissolving biomedicine capsules.
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