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In Fluctuation-induced current from freestanding graphene (peer-reviewed version on Phys. Rev. E, note: behind a paywall) Thiabado, et al, report the extraction of work from brownian motion. The experimental set up involves graphene in close but insulated contact with an electrode that charges a battery and a storage capacitor until a switch shunts the potential through a resistor. enter image description here

This seems to be a Feynman-Smoluchowski ratchet hence perpetual motion of the second kind. If so, where is the flaw in the experiment?

Nil Einne
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James Bowery
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2 Answers2

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Thibado "published" about this idea three years ago https://researchfrontiers.uark.edu/good-vibrations/ enter image description here https://youtu.be/wrleMqm3HiU

He now added complications (diodes etc) but that won't help.

The system with mechanical noise makes it a bit more complicated but not really different from a resistor with thermal noise. It is like trying to get energy from the thermal voltage of a resistor. Cannot be done.

Edit: there is an obvious source of energy in the schematic of their new preprint: that battery. I suspect that the bias voltage is the source of the power that they detect. (But I have not analyzed this in detail.)

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The interpretation is almost certainly wrong. A graphene film cannot "ripple" due to a static, spatially uniform temperature. It can only mechanically deform in response to a changing temperature or a temperature gradient. If all the calculations are done properly, the graphene film device will be determined to be a heat engine whose performance is consistent with the usual laws of thermodynamics. I can't state that from direct evidence (i.e., an experiment that measures temperature and entropy changes associated with this device), but the indirect evidence is overwhelming.

S. McGrew
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