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Demons can unleash arcane energies in physics as well as fantasy. The building of a real-life version of "Maxwell's demon" – which can turn information into useful energy – might mean that future nanomachines can be powered purely by information.

Conceived by James Clerk Maxwell in 1867, the demon exploits the random thermal motions of the microworld. It might watch a tiny ball on a spiral staircase, waiting for it to randomly hop up a step and then slam in a barrier to stop the ball moving down again. If the demon keeps doing this the ball keeps climbing. The potential energy of the ball could then be used to drive an engine.

Initially, it seemed as if Maxwell's demon was getting something for nothing, creating a perpetual motion machine, but later it became clear that the demon must expend some energy in getting information about these random motions, so it wouldn't break the laws of thermodynamics after all. But nobody was able to physically demonstrate the demon and find out for sure.

Now researchers in Japan led by Eiro Muneyuki of Chuo University in Tokyo and Masaki Sano of the University of Tokyo have used a tiny rotor and an electric field to construct a version of Maxwell's demon.

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Category: Science