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Fungi have always intrigued scientists and nature enthusiasts alike. This unique kingdom of life, more closely related to animals than to plants, includes an astonishing array of organisms. It encompasses everything from edible mushrooms to molds, single-celled life forms to the largest living organism on the planet, as well as pathogens that can cause diseases and remarkable species that produce medicinal compounds. Recently, researchers at Empa have unveiled yet another remarkable property of fungi: their ability to generate electricity.
As part of a three-year research initiative funded by the Gebert Rüf Stiftung’s Microbials funding program, scientists from Empa’s Cellulose and Wood Materials laboratory have successfully developed a functional fungal battery. While the electricity produced by these living cells is limited, it is sufficient to power devices like temperature sensors for several days. Such sensors have various applications, particularly in agriculture and environmental studies. The fungal battery’s most significant advantage is that it is entirely non-toxic and biodegradable, distinguishing it from conventional batteries.
Innovative Fungal Technology
Technically, what the researchers created is known as a microbial fuel cell, rather than a traditional battery. Microorganisms, like all life forms, convert nutrients into energy, and microbial fuel cells harness this metabolic process to capture some of the energy in the form of electricity. Historically, these cells have primarily utilized bacteria for power. “This is the first instance where we have successfully combined two different types of fungi to create a functioning fuel cell,” explains Carolina Reyes, a researcher at Empa. The unique metabolic processes of these fungal species work in harmony: on one side, a yeast fungus generates electrons while a white rot fungus on the opposite side produces an enzyme that helps capture and transfer these electrons out of the cell.
Instead of planting the fungi into the battery, they are integrated into the structure from the very beginning. The components for this fungal battery are produced using advanced 3D printing techniques. This method enables the researchers to design electrodes that maximize the fungi’s access to nutrients. To achieve this, fungal cells are mixed into the printing material, which poses its own set of challenges. “Finding an appropriate medium that allows the fungi to thrive is complicated enough,” notes Gustav Nyström, Head of the Cellulose and Wood Materials lab. “Moreover, the ink must be easy to extrude without harming the cells, while also being electrically conductive and biodegradable.”
Integrating Biology and Engineering
With their deep expertise in the 3D printing of soft, bio-based materials, the researchers managed to create an appropriate printing ink based on cellulose. Interestingly, the fungal cells can consume cellulose as a nutrient, aiding in the breakdown of the battery post-use. However, the researchers also incorporate simple sugars into the battery cells, which are the fungi’s preferred food source. “The fungal batteries can be stored in a dried condition and activated on-site simply by adding water and nutrients,” Reyes adds.
Although the resilient fungi can endure dry periods, working with living materials has introduced various challenges for the Empa team. This interdisciplinary project intertwines microbiology with materials science and electrical engineering. To analyze the fungal batteries effectively, microbiologist Reyes had to learn electrochemical methods and adapt those procedures for the specialized needs of 3D printing inks.
The research team aims to enhance the power and longevity of these fungal batteries and is exploring different fungi that may also contribute to electricity generation. “Fungi are still largely unexplored and underutilized, particularly in materials science,” Reyes and Nyström both assert.
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