Anthropocene

Mushroom skins could be the secret to recyclable electronics

The world generates over 140,000 tons of e-waste every day. This waste is complex and consists of many different materials, making it very difficult to separate and recycle.

Researchers have turned to the humble fungus for help. In a new one scientific advances Study shows how processed mushroom skin could be a biodegradable substrate for computer chips, bringing us one step closer to recyclable electronics.

Electronic circuits consist of multiple computer chips and other components that sit on circuit boards made of conventional plastic. These circuit boards are a major hurdle when it comes to recycling electronics, says Martin Kaltenbrunner of Johannes Kepler University in Austria. “They are difficult, if not impossible, to reuse or take apart. Often it is not economical to recycle them, so they are either incinerated or landfilled.”

Meanwhile, the world is producing more and more small electronics that don’t need to last too long. These include sensors, electronic labels for in-store products, and wearable health monitoring devices. Making degradable versions of these short-lived devices could be a big step towards sustainability. And a good place to start is the plastic circuit board.

Mushrooms are already used to make sustainable leather and styrofoam-like packaging materials. Kaltenbrunner and his colleagues accidentally came across fungus skins for printed circuit boards. One of his doctoral students is working on wood-mushroom composites for insulating materials. He found that Ganoderma lucidium Fungi form a compact protective skin around the wood chips on which they grow. He could peel off large sheets of this material that resembled thin sheets of paper.

Drying the sheets yielded a strong, flexible, and electricity and heat resistant material that was perfect for a circuit substrate. The material could be bent and folded more than 2,000 times without losing its electrical resistance.

The researchers were able to solder electronic components and construct metal circuits on the skin. They also made a largely biodegradable battery from the fungal material. Fungal skin soaked in a conductive liquid electrolyte was the battery’s central separator, with metal pastes on either side for electrodes. Its outer covering consisted of the dry skin of the fungus. It could power small devices like a Bluetooth module and a humidity sensor.

The fungal skin also hits the “sweet spot” of degradability, says Kaltenbrunner. Other naturally derived materials that either degrade too quickly or require industrial composting facilities to degrade. The fungal skin, on the other hand, “lasts a long time if kept reasonably dry, but in a normal household compost it would completely decompose in two weeks or less. No special facilities required. In addition, no post-processing or chemical treatment is required.”

Others have made biodegradable electronic substrates from paper and silk. But growing and processing silk for thin film is complex, while making paper is energy- and water-intensive. Making a ton of paper requires about 300 million liters of water and about 33 gigajoules of energy, Kaltenbrunner says, making it less than ideal for cheap, large-scale electronics.

Mushrooms, on the other hand, are easy to cultivate on scrap wood, and the skin grows naturally and doesn’t require much processing, he adds. “Our mushroom-based materials have the potential to be cost-effectively scaled to the needs of the everyday electronics industry, while being less resource and energy intensive than other approaches.”

The team is now looking for processing methods that will allow them to reliably grow uniform mushroom skins. And they also aim to combine the sustainable substrate with self-degradable electronic components to create fully biodegradable circuits.

Source: Doris Danninger et al. MycelioTronics: Mushroom mycelium for sustainable electronics. scientific advances2022.

Image © Anthropocene Magazine

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