“For decades, people have been envisioning that one day, we would have edible electronic devices to diagnose or treat disease. 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,” shared Christopher Bettinger, Ph.D. of Carnegie Mellon University who developed an edible battery that could help in the diagnosis and treatment of diseases.
The concept of ingestible devices is not a new concept since about 20 years ago, scientists created a battery-operated ingestible camera as a complementary tool to endoscopies, which captures places in the digestive system that traditional endoscopes cannot reach. It is meant to pass through the body and be excreted, with little risk in getting stuck in the gastrointestinal tract – but still a risk once it cannot find its way out.
Bettinger and his non-toxic, ingestible, edible battery. Source: Bettinger Lab
Bettinger’s design in making ingestible, degradable device relies on melanins and other naturally occurring compounds to answer toxicity issues. Melanins, commonly found in our skin, hair and eyes, absorb ultraviolet light to reduce free radicals and protect us from damage. But more than that, melanins also bind and unbind metallic ions, which qualifies them as battery. Bettinger’s team built on that idea and tested 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.
Hang-Ah Park, Ph.D., a post-doctoral researcher at CMU, said that the exact numbers depend on the configuration, but as an example, a 5 milliWatt device can be powered for up to 18 hours using 600 milligrams of active melanin material as a cathode. Its capacity is relatively low compared to lithium-ion, but it’s enough to power an ingestible drug delivery or sensing device.