The biobattery that needs to be fed

The biobattery that needs to be fed
by Robert Schreiber
Berlin, Germany (SPX) Jan 10, 2025

Fungi, a fascinating kingdom of life more closely related to animals than plants, display incredible diversity. They range from edible mushrooms to molds, single-celled organisms to the world's largest living entities, and from disease-causing pathogens to sources of vital medicines. Now, researchers at Empa have unlocked a new capability of fungi-generating electricity.

In a three-year research initiative funded by the Gebert Ruf Stiftung under the Microbials program, scientists from Empa's Cellulose and Wood Materials laboratory have developed a fungal-based microbial fuel cell. While these biobatteries generate modest amounts of electricity, it is sufficient to power devices like temperature sensors for several days. Such sensors are widely used in agriculture and environmental monitoring. The fungal battery stands out for being non-toxic and entirely biodegradable, setting it apart from conventional batteries.

Harnessing Fungi for Power

Technically classified as a microbial fuel cell, the fungal battery exploits the metabolic processes of microorganisms to convert nutrients into energy. Unlike traditional microbial fuel cells that use bacteria, this innovation employs two types of fungi to achieve its functionality. "For the first time, we have combined two types of fungi to create a functioning fuel cell," explained Carolina Reyes, an Empa researcher.

The design features yeast fungi at the anode, where their metabolism releases electrons. At the cathode, white rot fungi produce an enzyme that captures and transfers these electrons. This complementary metabolic relationship powers the battery.

3D Printing Revolutionizes Bio-Battery Construction

Rather than adding fungi to the battery post-production, they are integrated into the manufacturing process. The battery components are fabricated using 3D printing technology, allowing precise structuring of electrodes to optimize nutrient accessibility for microorganisms. To achieve this, fungal cells are incorporated into the printing ink, a complex task. "Finding a material conducive to fungal growth is difficult enough," said Gustav Nystrom, head of Empa's Cellulose and Wood Materials lab. "The ink also needs to be extrudable, electrically conductive, and biodegradable without harming the cells."

Empa's expertise in 3D printing bio-based materials enabled the creation of a cellulose-based ink that meets these criteria. The cellulose also serves as a nutrient for the fungi, aiding in the biodegradation of the battery after use. The battery is activated by adding water and simple sugars, its preferred nutrient source. "You can store the fungal batteries in a dried state and activate them on location by simply adding water and nutrients," Reyes added.

Bridging Biology and Engineering

Developing this innovative technology required bridging microbiology, materials science, and electrical engineering. Reyes, trained in microbiology, adapted electrochemical techniques to characterize the fungal batteries and optimize the 3D-printing process. Despite their robustness, working with living fungi presented unique challenges, especially in creating a system that could sustain the fungi during operation and ensure biodegradability after use.

Looking Ahead

Empa's team aims to enhance the fungal battery's performance and longevity while exploring additional fungal species suitable for electricity generation. "Fungi are still under-researched and under-utilized, especially in materials science," Reyes and Nystrom noted.

Research Report:3D Printed Cellulose-Based Fungal Battery