The researchers will present their work today at the 252nd National Meeting & Exposition of the American Chemical Society (ACS). ACS, the world’s largest scientific society, is holding the meeting here through Thursday. It features more than 9,000 presentations on a wide range of science topics.
«For decades, people have been envisioning that one day, we would have edible electronic devices to diagnose or treat disease," says Christopher Bettinger, Ph. D. «But if you want to take a device every day, you have to think about toxicity issues. That’s when we have to think about biologically derived materials that could replace some of these things you might find in a RadioShack.»
About 20 years ago, scientists did develop a
The camera and some implantable devices such as pacemakers run on batteries containing toxic components that are sequestered away from contact with the body. But for
«The beauty is that by definition an ingestible, degradable device is in the body for no longer than 20 hours or so," Bettinger says. «Even if you have marginal performance, which we do, that’s all you need.»
While he doesn’t have to worry about longevity, toxicity is an issue. To minimize the potential harm of future ingestible devices, Bettinger’s team at Carnegie Mellon University (CMU) decided to turn to melanins and other naturally occurring compounds. In our skin, hair and eyes, melanins absorb ultraviolet light to quench free radicals and protect us from damage. They also happen to bind and unbind metallic ions. «We thought, this is basically a battery," Bettinger says.
Building on this idea, the researchers experimented with battery designs that use melanin pigments at either the positive or negative terminals; various electrode materials such as manganese oxide and sodium titanium phosphate; and cations such as copper and iron that the body uses for normal functioning.
«We found basically that they work," says
Although the capacity of a melanin battery is low relative to
In parallel with the melanin batteries, the team is also making edible batteries with other biomaterials such as pectin, a natural compound from plants used as a gelling agent in jams and jellies. Next, they plan on developing packaging materials that will safely deliver the battery to the stomach.
When these batteries will be incorporated into biomedical devices is uncertain, but Bettinger has already found another application for them. His lab uses the batteries to probe the structure and chemistry of the melanin pigments themselves to better understand how they work.
