Scientists Create a Battery That Can Be Swallowed: It Powers a Medical Device and Then Dissolves

Scientists have developed a battery that can be swallowed together with a medical device. It can power electronics inside the body for several days and then gradually break down and be eliminated from the body. So far, the technology has only been tested in pigs, but in the future, such batteries could enable the use of temporary medical devices in the gastrointestinal tract without the need for surgery to remove them.

The findings were published in the journal Nature Chemical Engineering.

Conventional batteries remain one of the largest components of ingestible medical devices. They must also be hermetically sealed because the materials inside them can damage surrounding tissues. The new battery, by contrast, is made from components that gradually dissolve in the acidic environment of the gastrointestinal tract and are then safely absorbed by the body.

The battery consists of several layers. The negative electrode is made of a magnesium alloy, while the positive electrode contains molybdenum trioxide and activated carbon. Between them is a biodegradable electrolyte that enables the generation of an electric current. The scientists used cellulose nanofibrils as a binding material, making the structure thin, porous, and paper-like.

To prevent the battery from breaking down too quickly under exposure to stomach acid, the researchers coated it with beeswax. In some versions, they also used candelilla wax, which helped extend the battery’s operating life.

In laboratory tests, one version produced about 1.77 volts and could store and deliver 2 milliampere-hours per square centimeter, which is sufficient to power low-power electronics. A larger version produced about 1.84 volts and had a maximum capacity of 3.5 milliampere-hours.

The researchers then placed the batteries inside 3D-printed capsules and administered them to pigs. Both versions operated for up to three days, gradually losing voltage and capacity as they degraded.

The scientists used the batteries to power two experimental medical devices. The smaller battery powered a wireless radio-frequency identification (RFID) tag placed in the esophagus. It transmitted a signal over a distance of up to 1.5 meters and made it possible to track when the animals received medication.

The more powerful battery powered a swallowable capsule that stimulated the stomach using electrical impulses. As a result, the pigs’ blood levels of ghrelin, a hormone that stimulates hunger, increased. No visible tissue damage was detected at the site of stimulation.

However, not all components of the devices currently dissolve. The electronic circuit board used in the stomach-stimulation experiment did not degrade, but the animals naturally eliminated it from their bodies. According to the researchers, developing fully biodegradable devices would eliminate the risk of an individual component remaining in the gastrointestinal tract.