An edible battery gets its juice from food

Researchers have started crafting edible circuits and sensors that can be used in the body. But such devices need a power source to be effective. Now, a new rechargeable battery gets its juice from food (Adv. Mater. 2023, DOI: 10.1002/adma.202211400).

Such electronics could safely sense inside our bodies, for instance, tracking pH or temperature in the gut, says Mario Caironi, an electronics engineer at the Istituto Italiano di Tecnologia. “You don’t have to worry about the fate of this device,” he says. An entirely edible device could degrade in the body or be digested. That’s in contrast to ingestible electronics that contain potentially harmful components and need to be recovered before becoming electronic waste.

Caironi and his team used grocery items for several of their cell’s ingredients, including sushi seaweed and edible gold foil. For the battery’s energy-generating reactions, they looked to food-derived redox cofactors, such as the food additive indigo carmine. Redox cofactors are molecules that play roles in organisms’ biochemical energy generation, says Ivan K. Ilic, a chemist who was part of the work while at Istituto Italiano di Tecnologia.

For electrodes, the team loaded activated carbon with these redox-active molecules. They found they could generate a sufficiently high voltage using quercetin, a flavonoid found in foods such as capers, on the cathode and the B vitamin riboflavin on the anode. A piece of seaweed soaked in an electrolyte solution of an edible salt, sodium bisulfate, separated the electrodes. To collect the cell’s current, the team took inspiration from cake decorators, fixing delicate but highly conductive gold foil onto an ethyl cellulose film. Finally, they encased the cell in beeswax, which would protect it from the gastrointestinal tract’s acidic fluids, Caironi says.

The prototype operated at 0.65 V and produced a current of 48 μA for 12 minutes and could be recharged dozens of times, which may be necessary on a journey though the gut that could last a couple of days. Two cells in series lit an LED. “It’s not as powerful as a commercial battery, but the chemistry is there,” Caironi says.

“This is a very important demonstration,” says Mihai Irimia-Vladu, a materials engineer at Johannes Kepler University Linz who was not part of this work. The team “did an absolutely amazing job” identifying food components safe for consumption in relatively large amounts, allowing higher loading that can increase the battery’s capacity, he says. It’s a meaningful cell that could power electronics, he says, though it needs to be made smaller and easier to swallow.

The researchers are already working to boost capacity while shrinking the roughly 2 cm by 0.5 cm battery to a size that would easily fit in a pill, and they are working to integrate it into a proof-of-principle entirely edible device. “We can really make complex electrochemical devices using just everyday food,” Ilic says.