Circuit Design Claimed to Harvest Tiny But Infinite Power From Brownian Motion

At room temperature, micron-sized sheets of freestanding graphene are in constant motion, even in the presence of an applied bias voltage. University of Arkansas researchers collecting the displacement current using a nearby small-area metal electrode and present an Ito-Langevin model for the motion coupled to a circuit containing diodes. Numerical simulations show that the system reaches thermal equilibrium and the average rates of heat and work provided by stochastic thermodynamics tend quickly to zero. Power is dissipated by the load resistor, and its time average is exactly equal to the power supplied by the thermal bath. The exact power formula is similar to Nyquist’s noise power formula, except that the rate of change of diode resistance significantly boosts the output power, and the movement of the graphene shifts the power spectrum to lower frequencies. They have calculated the equilibrium average of the power by asymptotic and numerical methods. Experiments have proven the theory.

NOTE: These are big claims and the power levels must be very, very small. They will need millions of miniaturized circuits powering a capacitor to replace the battery for a tiny low power chip.

Harvesting energy from graphene is controversial because it disproves physicist Richard Feynman’s assertion that the thermal motion of atoms, known as Brownian motion, cannot do work. Thibado’s team found that at room temperature the thermal motion of graphene does induce an alternating current (AC) in a circuit, an achievement thought to be impossible.

Thibado’s group built their circuit with two diodes for converting AC into a direct current (DC). The diodes in opposition let current to flow both ways. There are separate paths through the circuit which produce a pulsing DC current that performs work on a load resistor.

On-off, switch-like behavior of the diodes amplifies the power delivered. It was previously expected to reduce power.

The power is not from heat differences as this would violate the second law of thermal dynamics.

The next goal is to store the energy in capacitors for later use. They need to miniaturize the circuit and patterning it on a silicon wafer or chip. If millions of these tiny circuits could be built on a 1-millimeter by 1-millimeter chip, they could serve as a low-power battery replacement.

SOURCES- University of Arkansas, Physical Review E – Fluctuation-induced current from freestanding graphene
Written By Brian Wang,

43 thoughts on “Circuit Design Claimed to Harvest Tiny But Infinite Power From Brownian Motion”

  1. The press release is terrible. Like really bad. It’s not perpetual motion – it’s just the fluctuation-dissipation theorem. The power associated with the fluctuating motion of their membrane (part of a capacitor) is the same Johnson noise power from the terminating resistor. By sticking diodes in the circuit they have changed the frequency response (power per bandwidth), but energy is conserved and at constant T no thermal energy is converted directly to useful work.

  2. About 4 milliwatts.
    13 milliwatts if you use the ceiling too.

    Average american home = 241.5 m^2 (google)
    walls are about ~40% of floorspace (Painting calculator) => 96.6 m^2 = ~96600000 mm^2
    96600000mm^2 * 0.00000000004 watts/mm^2 = 0.0039 watts

  3. It would seem to hinge on whether you need a separate switch for each circuit or can run them in parallel. If it can be parallelized then, as mentioned in the interview, if you could etch millions of these on a wafer a la transistors you might be able to get a low power device that runs for 'free' indefinitely.

  4. CompScientist's "That seems somewhat … unlikely." is a nice understatement.

    That said, I'll try to keep an open mind . . . after they can charge a battery and other non-affiliated scientists can reliably replicate this repeatedly.

    At the moment, the only way I can even begin to entertain a claim like this, in terms of my own world view, would be if our own universe (space-time) is capable of interacting selectively with the post heat-death attenuated waves of previous space-times, as I really don't see how we can ever reverse entropy on a non-local scale using just the space-time wave created at the Big Bang event.

    Convince me. Call me when you can charge your iPhone with it.

  5. Transistor without heat would definitely be a cool thing. But, my brain can't wrap itself around power generation that isn't consuming something. If its Brownian motion, then it's got to be removing energy (aka heat) from the particle motion. That says to me they are reducing the heat and storing it as electrons somewhere else. If they scale it up you have something that both cools and generates power, which would be a game changer. Definitely going to need to see this build in reality and independently verified before i'm a believer! Feynman is probably turning in his grave right now ;P

  6. Taking the quote from the article:

    Our model provides a rigorous demonstration that continuous thermal power can be supplied by a Brownian particle at a single temperature while in thermodynamic equilibrium, provided the same amount of power is continuously dissipated in a resistor.

    It doesn't sound like they've managed cooling, but I don't see why they can't use a transistor as the resistor. So, free computation without using extra power or generating extra heat.

    Which makes this an anti-entropy device?

  7. They need to hook some of these to an LED and have a conference. Its one thing to say Feynman was wrong, its another to unambiguously show it.

  8. The 2nd paragraph of the History section, which talks about Brillouin's electrical analog is particularly relevant:

    Léon Brillouin in 1950 discussed an electrical circuit analogue that uses a rectifier (such as a diode) instead of a ratchet. The idea was the diode would rectify the Johnson noise thermal current fluctuations produced by the resistor, generating a direct current which could be used to perform work.

    Which is more or less what they're doing here, except their noise current comes from a capacitor instead of a resistor. It continues:

    In the detailed analysis it was shown that the thermal fluctuations within the diode generate an electromotive force that cancels the voltage from rectified current fluctuations. Therefore, just as with the ratchet, the circuit will produce no useful energy if all the components are at thermal equilibrium (at the same temperature); a DC current will be produced only when the diode is at a lower temperature than the resistor.

  9. After reading part of the paper, there may be more to it than that. Something about the electron-phonon coupling in graphene making it oscillate in a certain way. Maybe not necessary, but convenient for this purpose (though their original purpose was to study those oscillations or some aspect of them, not generate power).

  10. Indeed, but you have to look at it more indirectly, also considering the medium in which this happens: There are no free lunches because Brownian motion is EXTERNALLY powered and there is no limit to that amount of (meagre) power if you space it out over time, which this circuit does. Besides that, the small amount of electrons being oscillated is far smaller in size and number, than the large amount of atoms which form the material matrix in which these electrons wiggle. So there is no free lunch, but the electrons do get a free ride in the backseat of the bus consisting of matter that is being shaken in the process of Brownian motion. The electron thus is a passenger on matter that is being waved, causing secondary motion, which is DC charge movement, which the capacitor and switching can sequestor until enough of it is built up to harvest in a meaningful amount to do a relevant amount of work.

  11. Maybe both are right: Feynman and these researchers.
    The Brownian Motion could not do work (in aggregate) but could help harvest ZPE.

    Apparently a lot of these new energy concept have something to do with micro/nano scale components and ZPE.

  12. As far as I can see, graphene isn't magical here, it's just light weight, strong, flexible and conductive. All those things improve the result.

  13. What I mean is that the amplitude (or maybe the frequency) of the motion will be smaller, not the duration. It has to move against an electric field, which is more difficult. There are no free lunches.

  14. Couldn't this also be used as a way to cool chips? If what we're looking at is removing power from the ambient temperature of the circuit. It seems to me that if you had enough of them, you could both recycle the energy on a chip and cool it at the same time, both reducing power consumption and increasing cooling. Although, IANAP and I don't know the order of power/heat we're talking about. It does seem fascinating 🙂

  15. Is graphene absolutely essential to this process? Or could something else be substituted? Otherwise, what makes graphene so special and unique for this purpose?

  16. This feels more like Maxwell's Demon, made from pieces of Graphene. Liquid/gas phase collisions of molecules are part of what temperature is – part of what a sink is. This is like extracting energy from a sink. Temperature is a macroscopic property, not a microscopic Brownian property. This is like going behind the scenes, or beneath the property of temperature, to extract energy from its underlying kinetic components.

  17. Why/how would the Brownian motion be attenuated, when it's an ambient energy drawn from the wider surroundings? Any effect on the overall sink is negligible, by definition. For all practical purposes, you should be able to continue drawing energy from the surroundings indefinitely.

  18. The animation looks like they need some external force to repeatedly push the blue graphene back and forth.

    That back and forth motion is supplied by the thermal Brownian motion. That's the big deal.

  19. The OP mentions 40pW. Now a picowatt is really small, but

    1. That is enough power to run a tiny electrical circuit of similar size to the generator circuit. Maybe a sensor or something.
    2. Because this is just electronics plus a graphene fragment, you can probably make a chip with a billion such generating circuits on it.
  20. The animation looks like they need some external force to repeatedly push the blue graphene back and forth. So it seems this mechanical work (supplied by some outside force) is being converted into electrical power. That's also what a piezoelectric crystal does. So it's not surprising, and not new. Maybe their system is a little more efficient than previous systems have been. So maybe that's their contribution.

    However, the article talks about it as if it disproves the assertion of Feynman (and all modern physicists) that you can't get work purely from thermal motion at a single temperature. Disproving that would mean disproving the known laws of thermodynamics and conservation of energy. That seems somewhat … unlikely.

    The article also says 

    The power is not from heat differences as this would violate the second law of thermal dynamics.

    But that's backwards. Getting power from temperature differences is allowed by physics. It's getting power purely from a single temperature that isn't.

    Since the animation and article seem to contradict each other, and since only one of them is consistent with the known laws of physics, I'm guessing that the animation is correct and the claims about contradicting Feynman are incorrect.

  21. Searching the web, I found one person asking if it was a 2nd level perpetual motion machine, but that turned out to be James Bowery, who posts here too, so I'll let him report if any answer turns up.

  22. According to the animation, the battery finishes the cycle with the same charge as what it started with.
    So you could substitute another capacitor for the battery and get your perpetual motion machine.

    "An energy-harvesting circuit based on graphene could be incorporated into a chip to provide clean, limitless, low-voltage power for small devices or sensors,"

    said Paul Thibado, professor of physics and lead researcher in the discovery.

    He then mentions Maxwell's daemon, but I'm not grasping why this circuit gets away with it.

    Worst case scenario, they've accidentally worked out how to make daemons and Arkansas is about to suffer a hellmouth invasion. It's 2020 so there is a 10% chance this is how it goes down.

  23. Perpetual motion machine of the second kind produces
    work from a single heat source – and that seems to be the case here. You cannot do that, cause it violates the second law of thermodynamics.

  24. It is not really a perpetual motion machine. Brownian motion is a thermal effect from liquid or gas-phase collisions of molecules with the graphene or intrinsic movement of the carbon nuclei in the graphene if the system is in a vacuum at room temp . It wouldn't work at low (cryogenic) temperatures. This is more like a thermoelectric heat pump, on a micro scale.

  25. Let me see if I understand their little animation… The graphene sheet and metal plate form a capacitor, which is governed by C = q/V = εA/d. When the graphene sheet bends closer to the electrode (smaller d), the capacitance C is increased, so to maintain the same voltage V, it has to draw in charge q from the battery (which is probably just a pre-charged capacitor) through the left circuit.

    When the graphene bends away, the capacitance is decreased, so charge has to flow out, recharging the battery. But this can only happen through the right circuit (because of the diodes), so it also charges the main capacitor. The next cycle this repeats again, and the diodes make sure that the main capacitor doesn't discharge. Finally, they flip the switch to discharge the main capacitor via the work load.

    If the main capacitor and diodes weren't there, this would just be an oscillator, transferring charge back and forth between the battery and graphene, with no work being done (neglecting heat dissipation through the wires). But to charge the main capacitor requires extra work. That comes from the graphene bending away against the electrical field when it's charged. So we have heat -> Brownian motion -> mechanical work against an electric field -> electric energy.

    With the voltage in place, I expect the Brownian motion will be attenuated. The electric energy comes at the cost of this mechanical energy. That may also be a useful effect when Brownian motion is unwanted.


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