Your next phone could be made of mushrooms

As electronics like laptops, cellphones, and smartwatches become ever-more integral to our daily lives, a growing mountain of electronic waste looms on the horizon — and it’s quickly becoming too great to ignore. But most of this waste is hard to recycle because it contains toxic components and is tough to break down.

Now, some engineers hope nature can help solve our e-waste problem: enter biodegradable electronics (also called “soft” or “transient” electronics).

The field of soft electronics is still fairly young, but it could make tech trash a thing of the past. “It’s better to think about sustainable materials and approaches early on, because in the end, we’ll end up with a lot of waste,” says Martin Kaltenbrunner, an electronic engineer at Johannes Kepler University in Linz, Austria, and one of the study’s authors.

To tackle this challenge, Kaltenbrunner and his team are developing a base for flexible electronics made from the skin of mycelium, the chitin- and cellulose-rich stuff that makes up most of a mushroom’s body, as reported last week in Science Advances.

This base, also known as a substrate, is typically used to insulate and cool electronic circuits. According to the new study, mushroom skin could take the place of non-recyclable plastic polymers in future substrates.

Here’s the background — Globally, people toss out approximately 140,000 tons of e-waste every single day. “That’s the combined mass of fourteen Eiffel Towers,” Kaltenbrunner says.

Some of this rubbish contains potentially toxic materials, such as lead, cadmium, and beryllium. And much of it is composed of difficult-to-break-down material, like hard plastics and rubbers. E-waste recycling exists, but by and large, its efficiency is relatively low because devices can be complex and consist of many different components.

What’s more, people tend not to capitalize on it; only about 20 percent of all e-waste was recycled in 2019. This has lead some experts to propose a different route: Why not make electronics compostable?

The idea to switch to biodegradable electronic devices has floated around for at least a decade. Since then, scientists have tinkered with crafting electronics from paper, silk, and electron-transporting bacteria. But these solutions have either had limited conducting potential or have proven too resource-intensive to produce on a large scale.

Now, mushroom-derived substrates could provide a scalable, eco-friendly solution.

What’s new — The new mycelium-based base is easy to grow; all it needs is some decaying wood and the right spores. And, according to Kaltenbrunner, it’s just as simple to prepare. “It turns out you don’t need to do a lot of things to use it for electronics — you just need to dry it,” he says.

In order to cultivate the fungus, the researchers first seeded dead hardwood with Ganoderma lucidum spores, a popular mushroom that is also known as reishi. It’s often sold in “grow your own” kits and is valued for its health properties by traditional Chinese medicine.

Then, they carefully regulated the amount of light and carbon dioxide in a dark, temperature-regulated space as the fungus grew in order to prevent them from forming fruiting bodies — this would have roughened up their otherwise smooth skin. Finally, they harvested the outer layer of mycelium from the young mushrooms.

Once dry, these skins can handle temperatures up to 482 degrees Fahrenheit. The team coated their fungal material in ultra-thin layers of metal (all of which can theoretically be recycled) and paired it with traditional electronics components to create sensor boards — they also used the skin to make some battery components.

What’s next — To harness the full potential of mycelium-based electronics, scientists will first need to work out a few kinks in the cultivation process. “The growth process itself seems fairly scalable,” Kaltenbrunner says. “But it’s not always uniform.”

Some of the skins that Kaltenbrunner’s lab harvested were a nice, consistent shape, but others were too lumpy or uneven to use without considerable modification. To create reliable electronics, they will need to find a way to grow mycelium that ends up looking the same every time.

Even if mushroom substrates and battery materials prove to be a success, Kaltenbrunner cautions, it won’t completely solve the e-waste problem. After all, engineers will still need to use some non-fungi components in the final product, like battery cathodes and anodes. “You cannot simply replace the electronics industry using mushrooms,” he says.