Open a phone, a remote, an electronic toy. Inside, always the same green plate. That's a printed circuit board — and the world throws away enough of them to hit 82 million tonnes of electronic waste a year by 2030.
That plate is two layers. Underneath, a rigid support made of glass-fibre-reinforced epoxy resin: it does nothing electrical, it just holds everything in place. On top, a thin layer of copper, etched into tracks, carrying the current and the signals.
Copper, we know how to recycle. The epoxy support, we don't. It doesn't recycle, it doesn't degrade, it stays.
Replacing the plate
A team at TU Bergakademie Freiberg went after that bottom layer.
Their raw material is a waste product: mycelium from Aspergillus niger, the fungus used industrially to make citric acid — the stuff in your soft drinks and household cleaners. Once fermentation is done, that biomass goes in the bin. By the thousands of tonnes.
The researchers mould it, air-dry it, and end up with a rigid 5-millimetre plate, as dense as a conventional circuit board. They etch copper on top, solder the components by hand. It works.
To be clear from the outset: the signals don't travel through the fungus. Mycelium replaces the support, not the tracks. But that's exactly the point of a first step — a different way of designing a circuit board. Yesterday these boards were assembled, today they're printed, tomorrow they could be grown.
And the fungus brings two things epoxy doesn't.
It composts. At end of life, the plate returns to the soil and the components come off intact. Carbon footprint: up to 56% less CO₂.
It doesn't burn. In a device under power, everything heats up: one short circuit, one overheat, and the support can catch fire and spread it to the rest. That's why conventional circuit boards are loaded with brominated flame retardants — effective, but among the most problematic substances in electronic waste. Mycelium is naturally hard to ignite: the nitrogen in its chitin does the job on its own. No additives.
Why this speaks to us
First, a coincidence: them in Freiberg, Germany. Us in Fribourg, Switzerland.
Then, an ambition. Our circuit boards pick up the electrical activity of mycelium. Long term, we want a system that can go straight into the soil — forests, farmland — and give farmers and researchers what no soil test shows them: what is actually happening under their feet, in real time.
Buried electronics raise a question others don't have to ask: what does it leave behind?
It's hard to measure an ecosystem while contaminating it. So a board that composts isn't a laboratory curiosity to us. It's a piece of the system we want to build.
Our sensors will spend their working lives surrounded by mycelium. One day, they might be made of it.
Source: Oehlsen et al., "From biotechnological residues to biodegradable printed circuit boards," Cleaner Materials (2026), TU Bergakademie Freiberg. Spotted via Chemical & Engineering News.