Scientists create fungal battery that needs feeding – then eats itself

Fungi could be used to power batteries in remote regions thanks to a new breakthrough by Swiss researchers.

Their fungal battery invention is 3D-printed – with fungal cells mixed into the printing ink – and has the unique advantage of being biodegradable. Once it’s served its purpose, the battery digests itself from the inside.

It adds to the growing body of research using fungi – a vast and “under-utilised” kingdom of life – to make everything from our clothes and homes, to meat alternatives. 

Here’s how the fungal battery, developed at the Swiss Federal Laboratories for Materials Science and Technology (Empa), is able to generate electricity.

Meet the living battery that needs feeding

Strictly speaking, Empa researchers explain, the battery is a microbial fuel cell.

Like all living things, microorganisms convert nutrients into energy. Microbial fuel cells make use of this metabolism and capture part of the energy as electricity. 

“For the first time, we have combined two types of fungi to create a functioning fuel cell,” says Empa researcher Carolina Reyes.

On the negative (or anode) side of the ‘battery’ is a yeast fungus whose metabolism releases electrons. It is complemented by a white rot fungus on the positive (cathode) side which produces a special enzyme, allowing the electrons to be caught and conducted out of the cell. 

The fungi feed on simple sugars, which are added to the battery cells. “You can store the fungal batteries in a dried state and activate them on location by simply adding water and nutrients,” explains Reyes.

How are fungal batteries made?

The fungi are not “planted” into the battery, so to speak, but are part of its material foundation from the start.

It is 3D printed to structure the electrodes in a specific way that gives the microorganisms easy access to the nutrients. Fungal cells are mixed into the printing ink – no mean feat for the cross-disciplinary researchers.

“It is challenging enough to find a material in which the fungi grow well,” says Gustav Nyström, head of Empa’s Cellulose and Wood Materials lab. 

“But the ink also has to be easy to extrude without killing the cells – and of course we want it to be electrically conductive and biodegradable.”

Thanks to their laboratory’s extensive experience in 3D printing of soft, bio-based materials, the team were able to produce a suitable ink based on cellulose. The fungal cells can even use the cellulose as an additional nutrient, and so help to break down the battery after use. 

Where could fungal batteries be used?

Big mushroom-powered electronics are still a stretch, as these living cells do not produce a great deal of electricity.

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But they could supply enough to power a temperature sensor for several days, for example, for agriculture or research in remote regions.

And the researchers are yet to get to the bottom of fungi’s full potential.

“Fungi are still under-researched and under-utilised, especially in the field of materials science,” agree Reyes and Nyström.

The researchers now plan to make the fungal battery more powerful and longer-lasting – and to look for other kinds of fungi that could supply electricity. 

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