Researchers at Empa have developed an innovative "fungal bio-battery" through 3D printing. While the energy output is modest, the potential is intriguing
3D printing technology has just crossed a new frontier: fuel cells. A team of scientists in Switzerland has created special printed fuel cells based on cellulose and fungi.
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Microbial Fuel Cells: New Progress
We are now exploring the field of microbial fuel cells or “bio-batteries,” devices that utilize microorganisms to oxidize a “fuel” – typically sugars or acids – and release electrons.
The idea behind microbial fuel cells dates back to the early 20th century, but to this day, optimizing their performance remains an ongoing challenge.
Nonetheless, their potential for low-power energy production – particularly for applications like diagnostic devices, remote sensing, or environmental monitoring – continues to draw significant research attention. The goal is to power future green electronics in a simpler and more sustainable way.
New Printed Fuel Cells Made from Mushrooms
The fuel cells created at the Swiss Federal Laboratories for Materials Science and Technology (Empa) offer several advancements over previous studies. Unlike conventional bio-batteries, they do not use bacteria but instead rely on two types of fungi: Saccharomyces cerevisiae (baker’s yeast) and Trametes pubescens (white rot fungus).
“For the first time, we have combined two types of fungi to create a working fuel cell,” says Empa researcher Carolina Reyes. The metabolic processes of these two species complement each other: on the anode side, the yeast releases electrons by oxidizing the fuel, while the cathode is colonized by the white rot fungus, which uses a dedicated enzyme to capture the electrons.
Another innovation: the researchers used 3D printing to create these new fuel cells. Specifically, they developed inks by combining the fungi with a sterile cellulose solution containing carbon black, graphite flakes, glycerol, and nutrients. This approach allows them to use only the necessary amount of material to create complex structures.
The Advantages of Using Fungi in Bio-Batteries
There is an additional benefit related to using fungi: “The fungal batteries can be stored in a dried state and activated on-site simply by adding water and nutrients,” Reyes explains.
How Much Power Do the Printed Fuel Cells Produce?
A single bio-battery has a maximum power density of 12.5 μW/cm² and a maximum current density of 49.2 μA/cm². When tested, the printed fungal fuel cells produced between 300 and 600 mV over several days. For the researchers, connecting four of these cells would already be enough to power a small sensor for 65 hours.
Moreover, they explain that it’s possible to build a fully biodegradable fungal fuel cell using beeswax and a cellulose proton-exchange membrane.
What’s Next?
The next steps involve making the device more powerful and durable, as well as exploring other types of fungi that could be suitable for this purpose.
The research was published in ACS Sustainable Chemistry & Engineering (2024). DOI: 10.1021/acssuschemeng.4c05494
