Scientists have developed an ingestible battery that can power medical devices inside pigs for up to three days, a step toward potential human use. The paper-based battery, safely broken down in the animals' bodies, could help with drug release and appetite regulation, researchers said.

The development is part of a wider effort to deploy innovations such as tiny robots in the human body. "This moves the technology beyond a materials demonstration toward an integrated biomedical system," said Giovanni Traverso, research leader and engineering professor at the Massachusetts Institute of Technology. The researchers are working with a partner to make prototypes for human use for a clinical trial due to start in about two years.

The battery was made using magnesium–molybdenum trioxide, encapsulated in melted beeswax and inserted by oral endoscopy into the stomachs of live swine. It powered a wireless tag in the pigs' oesophagi that communicated with a receiver 1.5 metres away, according to a paper published in Nature Chemical Engineering on Monday. The battery also provided energy for a capsule that electrically stimulated the stomach for 20 minutes.

While the battery itself was bioresorbable, the circuit board used for stomach stimulation was not and was excreted naturally. Materials exist that could make more circuitry bioresorbable, Traverso said. Other next steps include larger safety studies, consistent manufacturing, and testing in broader gastric environments.

Stomach disorders such as gastritis are common worldwide. Researchers not involved said the system seemed a feasible way of controlling and monitoring drug delivery. "The study offers a promising avenue towards improved transient electronic devices," said Micaela Matta, senior lecturer at King's College London.