Researchers in Switzerland develop biodegradable fungi battery

Researchers in Switzerland are developing a biodegradable battery made from mushrooms. At Empa, a 3D printer has combined two types of mushroom to create a small living cell that generates electricity.
The academics responsible report a possible application for non-toxic power supply in simple measuring devices such as the temperature sensors used in agriculture or environmental research. After supplying temperature sensors with power for a few days, the organic batteries would decompose.
Strictly speaking, the battery is a microbial fuel cell. The two types of fungi produce different enzymes and degradation products during metabolism. On the anode side there is a yeast fungus whose metabolism releases electrons. The cathode consists of white rot fungi – velvet trametes. The latter produces an enzyme that can capture the electrons from the yeast metabolism, the researchers claim.
The battery is manufactured by 3D printing with the fungi mixed into the printer “ink.” The active components of the battery are, thus, structural components. “It is challenging enough to find a material in which the fungi grow well,” said Gustav Nyström, head of the Cellulose & Wood Materials laboratory at Empa. “But the ink must then also be easy to extrude without the fungal cells dying – and of course it should also be electrically conductive and biodegradable.”
A cellulose-based ink met the requirements by providing nutrients for the fungi, making the device biodegradable. To ensure the battery does not degrade too quickly, the researchers added sugar molecules. Those are broken down by the fungus before the ink is metabolized. The cellulose structure, with the fungi and sugar molecules, is covered in beeswax and equipped with two copper contacts.

For the battery to start generating electricity, the fungi need water. This means the device can be stored in a dried state without the mushroom metabolizing the sugar or ink. The battery is activated by adding water, said Nyström.
The Empa team now wants to identify new fungi, materials, and inks to make the battery more compact and powerful, potentially expanding its application.
From pv magazine Deutschland.