Well, this is straight out of the Department Of Things I Did Not See Coming.
Where to begin?
So, have you ever pulled a giant fungus off of a tree in the forest, turned it over, and been able to draw on the bottom of it? I used to do that all the time when I visited friends in the Adirondacks years ago.
If you draw on the underside with your fingernail, a stick, or anything else you can scratch it with, the whitish surface turns permanently brown. You can then display your work of art on the fireplace mantel or wherever you like, and the design lasts indefinitely. That’s why this fungus, Ganoderma applanatum, is known as “artist’s bracket”. It’s found all over the world.
It’s a “white-rot” fungus because it can degrade lignin, a tough structural component of wood, and leave behind a bleached appearance. This is normally deemed a problem, especially if you’re a tree, but a group of Swiss researchers turned it into an advantage that’s almost too wacky to be believed. They let you know all about it in the March 10 issue of Science Advances.
A key facet of this is that — believe it or not — wood is a piezoelectric material. That means that when you apply pressure to it, a voltage develops across it. To illustrate this phenomenon in quite exaggerated terms:
Usually piezoelectric materials are crystals of some kind (like quartz and tourmaline), and squeezing them distorts their crystal structure and therefore alters the distribution of electrical charges inside them. By squeezing, you’re just converting one kind of energy (mechanical) into another (electrical). No magic tricks required. But still a little weird.
Wood has crystalline cellulose in it, and this is what the authors say is mostly responsible for the piezoelectric properties of wood. But wood, and many other piezoelectric materials, are obviously pretty difficult to squeeze. You really have to push on them hard to see any distortion — and thus any meaningful voltage.
That’s where the white-rot fungus comes in!
You can certainly use industrial chemicals to blast the lignin out of wood (a note on that down in the comments), but then you’ll have chemical waste like ethylene glycol, bleach, and sulfuric acid, and you’ll need to heat the whole process up to over 300°F.
White-rot fungi are happy to do this for you at room temperature and with no chemical waste; you just have to wait a few weeks. And when the fungi are done feasting on the wood, you simply brush them off the surfaces, and you find that the wood is much more pliable, almost spongelike.
That’s what our Swiss researchers did with artist’s bracket, for a scheme that looks like this:
The piezoelectric effect of the wood was increased 55 times by this fungal treatment, because the authors went from barely being able to indent the surface to easily compressing a whole bunch of layers at once. So with this new capability in hand, they hooked up a small group of cubes of treated wood to an LED light — inside a cute little house model, no less! — and when someone pressed down on the cube, the light went on!
So let’s review: You chew up some wood with fungus, press down on it, and it makes stuff light up. Nothin’ more to see here!
The authors were able to show that stringing multiple cubes together increased the voltage and current they could generate, in a pretty additive fashion. These aren’t huge bursts of power — we’re talking about one volt or so for this little block, and a current measured in nanoamps.
But that’s pressing once on a little square with your fingers. The bigger idea here is that if your floors have this under them, and you keep walking on them, you could store up a decent amount of energy. You could charge your phone, for example, by walking around for a while. We can envision areas with lots of foot traffic, like a building lobby or train station (or “ballrooms”, as the authors adorably suggest), generating a decent amount of usable energy this way.
People have recently had the idea to exploit this with pavement, too, so as heavy cars continually roll over a strip of reasonably pliable piezoelectric material, you’re actually starting to talk about decent utility, like lighting up the bridge the cars are rolling across.
In the meantime, though, there have got to be a bunch of fun little applications for this. While we’re on ballrooms, how about a Saturday Night Fever-type dance floor that illuminates itself? Or one of those giant floor pianos, like in Big?
Well, maybe those are for Travolta and Hanks. But what about me? What could I do with a squishy little cube that generates a voltage? I’m thinking about my doorbell….