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taylorvich writes:

https://physicsworld.com/a/mushroom-based-substrates-create-flexible-and-sustainable-electronics/

Fungal mycelium skins can be used as substrates for electronic devices, physicists and materials scientists in Austria have shown. The team used the thin skins to create autonomous sensing devices consisting of mycelium batteries, a humidity and proximity sensor, and a Bluetooth communication module. As well as providing a flexible surface for electrical circuits to be patterned on, the skins are biodegradable and could help cut electronic waste.

The researchers produced the mycelium skins from the fungus Ganoderma lucidum, which grows on dead hardwood in mild temperate climates. To create electronic circuits, they used physical vapour deposition to place a thin layer of copper and gold on the skin. Metal was then removed from this surface layer via laser ablation, leaving behind conducting paths. The researchers named this novel approach to creating flexible and biodegradable electronics "MycelioTronics", describing their work in Science Advances.

While working on mushroom-based materials for building insulation, Kaltenbrunner and his colleagues noticed that the fungi were producing a dense and compact skin of mycelium, which is a network of fungal threads. These skins looked like paper and the scientists wondered if they could be used for flexible circuit boards.

The team grew mycelium skins by covering moist beech wood shavings inoculated with Ganoderma lucidum with a polyethylene separator grid and storing them at 25°C. After sufficient fungal growth, the separator was ripped off the substrate and the mycelium skin was carefully peeled off the separator. The wet mycelium was then dried and compressed to produce the final skins.

After deposition and laser ablation of the metal layer, the researchers tested the resulting mycelium circuit boards. They found that that they had high conductivity and thermal stability, and were able to withstand around 2000 bending cycles before the metal film started to crack and electrical resistance increased. The skins could also be folded several times with only moderate increases in resistance.

Next the researchers created a flat, 2 cm2 mycelium battery, using a mycelium skin soaked in a highly ion-conducting electrolyte solution (ammonium chloride and zinc chloride) as the separator, and two mycelium skins as the outer casing. This structure results in a high percentage of the battery being biodegradable, they claim.

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