Swiss research team develops living battery from fungi

A team of researchers at the Swiss Federal Laboratories for Materials Science and Technology (Empa) has devised a new type of energy supplier: a 3D-printed battery made of cellulose that is based on the metabolism of fungi and biodegrades over time.

Don't worry, you don't need to put mushrooms in your mobile. The aim of the research is to develop more sustainable solutions for monitoring environmental conditions. The battery does not provide much energy. However, it should be enough to power temperature sensors for monitoring remote forests or fields for a few days, for example.

How does this "mushroom battery" work?

The fungal spores are integrated into cellulose-based, conductive inks. This mass can be used with a 3D printer to create electrodes on which the fungi can multiply. The fungus Saccharomyces cerevisiae (a yeast) grows on the anode side, releasing electrons through its metabolism. The cathode is formed by Trametes pubescens (a white rot fungus), which captures the electrons. This creates a small current flow - the researchers refer to this as a microbial fuel cell.

The researchers state that the battery can produce between 300 and 600 millivolts over several days and deliver three to 20 μA (microamperes). Four of these batteries connected in parallel should be able to operate an energy-saving sensor for up to 65 days. During this time, it can collect data on temperature, humidity or CO2 concentration. However, the sensor that powers the battery is not biodegradable.

To measure the battery performance, the electrodes were housed in a non-degradable Plexiglas chamber. In practical applications, however, a housing made of natural beeswax is used. This can decompose completely: After three weeks, only fragments were left in tests. Shellac, a natural resin produced by lice, is used as an adhesive to secure the individual components in the housing.

What other research is there in this area?

The background to the research is the high demand for electronic devices for environmental monitoring - for research as well as for agriculture. Sustainable and efficiently producible solutions should reduce the amount of non-recyclable electronic waste generated.

Microbial fuel cells are not a new invention. They also utilise photosynthesis, for example. Fungal fuel cells are also nothing new, but according to the authors of the study, they have succeeded for the first time in combining two types of fungi and utilising their different metabolic capabilities. Such fuel cells are also generally suitable for biomedical diagnostic applications (e.g. endoscopic diagnostic capsules in the stomach or intestine).

Further information can be found here. You can read the full study here.