Summary
Researchers tested a biodegradable battery made from body-compatible materials in two swallowable devices: an RFID transmitter and a stomach stimulator. The battery began breaking down in simulated gastric fluid within two weeks and dissolved completely after several months.
A biodegradable battery built for use inside the digestive tract has powered two swallowable medical devices in pigs: one that transmitted data using radio-frequency identification (RFID), and another that electrically stimulated the stomach. The battery began breaking down within two weeks in simulated gastric fluid and completely dissolved after several months.
The work is a preclinical demonstration of a power source designed to avoid leaving conventional battery materials inside the body. Its possible future uses include ingestible devices that monitor health and temporary devices that deliver electrical stimulation.
A battery designed to break down in the digestive tract
Conventional batteries can create risks if an ingestible device breaks open. Leaking chemicals may cause burns, while toxic metals, organic electrolytes and fragments of plastic casing can pass through or accumulate in the body.
The researchers therefore redesigned the battery around materials intended to be biodegradable or compatible with the body. Its electrodes use magnesium and molybdenum trioxide. Magnesium and molybdenum are metallic micronutrients needed by the body in small amounts, and the researchers found that the combination produced enough voltage to operate electronic components.
The battery uses a biodegradable ionic liquid as its electrolyte. In a battery, the electrolyte enables charged particles to move between the electrodes while the electrochemical reaction produces electrical power. The researchers selected the ionic liquid instead of buffered saline, which has performed poorly in some earlier biocompatible battery designs.
The packaging is also part of the design. A cellulose-based coating, inspired by edible rice-paper wrappers, holds the battery components together and dissolves over time. A beeswax layer slows the effect of stomach acid, allowing the battery to function before it breaks down.
Tests in simulated gastric fluid and pigs
In laboratory tests using simulated gastric fluid, the battery started to come apart within two weeks. It was fully dissolved after several months. The researchers then combined it with other fully biodegradable, non-toxic electronics and placed the systems inside gel capsules for tests in pigs.
The first capsule contained an RFID tag. Signals from the tag were detected by a reader outside the animals' bodies, demonstrating wireless transmission from inside the digestive tract.
The second device was introduced into the pigs' stomachs through endoscopy. Electrical stimulation caused an increase in the level of ghrelin, a hormone involved in regulating hunger. The result shows how a temporary ingestible power source could support an electroceutical device aimed at influencing the gut–brain connection.
Why ingestible power matters
Many swallowable medical devices need to operate only for a limited period before passing through the digestive system. A battery that can provide power and then break down could reduce the hazards associated with retrieving a device or leaving behind a conventional battery if its casing fails.
The researchers also envisage applications beyond short-lived diagnostic capsules. Similar materials could eventually power implantable systems that deliver electrical impulses to treat disease, although the reported work concerns simulated fluid and pig experiments rather than human treatment.
The stomach-stimulation approach is being explored as a possible way to regulate digestive activity and may be less invasive than procedures such as bariatric surgery or permanent implants. Its medical value will depend on the performance, duration and safety of each specific device in further animal and human studies.