According to a study published in ACS Sustainable Chemistry & Engineering, researchers from Empa’s Cellulose and Wood Materials laboratory created a functional fungal battery for a three-year research project funded by the Gebert Rüf Stiftung’s Microbials funding program.
Fungi are still underresearched in the field of materials science. Image Credit: Empa
A battery that needs feeding rather than charging? This is precisely what Empa researchers accomplished with their 3D-printed, biodegradable fungal battery. The living battery could power sensors for agriculture or research in remote areas. Once the work is completed, it digests itself from within.
Although the electricity the living cells produce is low, running a temperature sensor for a few days is sufficient, for instance. Environmental research and agriculture both make use of these sensors. The fungal battery’s greatest benefit is that it is biodegradable and non-toxic in contrast to traditional batteries.
Fungi from the Printer
The cell is technically a microbial fuel cell rather than a battery. Microorganisms use nutrients to create energy, just like any other living creature. Utilizing this metabolism, microbial fuel cells convert some of the energy into electricity. Up to this point, they have primarily been driven by bacteria.
For the first time, we have combined two types of fungi to create a functioning fuel cell.
Carolina Reyes, Researcher, Empa
The metabolisms of the two species of fungi complement one another. On the anode side is a yeast fungus whose metabolism produces electrons. A white rot fungus colonizes the cathode, producing a particular enzyme that captures electrons and conducts them out of the cell.
Fungi are not “planted” into the battery; they are an inherent cell element. The components of the fungal battery are created via 3D printing. This allows the researchers to design the electrodes so that microorganisms can access nutrients as easily as feasible. To accomplish this, fungal cells are incorporated into the printing ink.
It is challenging enough to find a material in which the fungi grow well. 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.
Gustav Nyström, Head, Cellulose and Wood Materials Lab, Empa
Microbiology Meets Electrical Engineering
Thanks to their laboratory’s extensive experience in 3D printing of soft, bio-based materials, the researchers were able to produce a suitable ink based on cellulose. The fungal cells can even use cellulose as a nutrient, which helps break down the battery after use. However, their preferred nutrient source is simple sugars added to the battery cells.
Reyes added, “You can store the fungal batteries in a dried state and activate them on location by simply adding water and nutrients.”
Working with the living materials presented several difficulties for the researchers, despite the fact that the robust fungi endure such dry times. Electrical engineering, materials science, and microbiology are all included in this multidisciplinary research. Reyes, a skilled microbiologist, had to master electrochemistry techniques and modify them for 3D-printing inks to define fungal batteries.
The researchers now intend to increase the fungal battery’s strength and durability as well as explore other fungi species that could be used to generate electricity.
Reyes and Nyström agreed, “Fungi are still under-researched and under-utilized, especially in the field of materials science.”
Journal Reference:
Reyes, C., et. al. (2024) 3D Printed Cellulose-Based Fungal Battery. ACS Sustainable Chemistry & Engineering. doi.org/10.1021/acssuschemeng.4c05494