Ingestible sensor is powered by stomach acid

According to the team the system is able to generate enough power to run small sensors or drug delivery devices for extended periods of time, and could lead to novel ways of monitoring patient health and treating disease.

Ingestible medical devices are usually powered by small batteries, but these self-discharge over time and can pose safety risks for patients.

In an effort to develop an alternative approach the team took their initial inspiration from the so-called lemon battery, a simple voltaic cell consisting of two electrodes stuck in a lemon. The citric acid in the lemon carries a small electric current between the two electrodes.

To replicate that strategy, the researchers attached zinc and copper electrodes to the surface of their ingestible sensor. The zinc emits ions into the acid in the stomach to power the voltaic circuit, generating enough energy to power a commercial temperature sensor and a 900-megahertz transmitter.

In tests in pigs, the devices took an average of six days to travel through the digestive tract. While in the stomach, the voltaic cell produced enough energy to power a temperature sensor and to wirelessly transmit the data to a base station located 2 meters away, with a signal sent every 12 seconds.