We never know exactly what to make of university press releases, as we see plenty of them with breathless claims of new batteries or supermaterials, but then we don’t see much else. Sometimes, the claims in the press release don’t hold up in the paper, while other times the claims seem to be impractical for use in real life. We aren’t quite sure what to make of a press release from the University of Arkansas claiming they can draw current from a sheet of freestanding graphene purely from its temperature fluctuations.
The press release seems to claim that this is a breakthrough leading to “clean, limitless power.” But if you look at the actual paper, normal room temperature is causing tiny displacements in the graphene sheet as in Brownian motion. A scanning tunneling microscope with two diodes can detect current flowing even once the system reaches thermal equilibrium. Keep in mind, though, that this in the presence of a bias voltage and we are talking about nanometer-scale displacements and 20 pA of current. You can see a simple video from the university showing a block diagram of the setup.
It seems that the news here is that current is flowing in a thermally stable system without violating the second law of thermodynamics. The innovation, apparently, is the idea of using two diodes to harvest both positive and negative fluctuations. Not much power, though. The press release talks about millions of these tiny circuits could serve as a low-power battery replacement.
There are still some pretty mysterious comments in the press release about the change in resistance of the diodes adds “an extra factor to the power,” and that “switch-like behavior of the diodes actually amplifies the power delivered…” We will have to wade through the math in the paper to see if we can figure out what any of that means.
We hear about exciting new things graphene will do all the time. We just don’t see it much in the wild, at least not yet. All this talk of graphene and diodes made us remember that you can create PN junctions in graphene.