Long term Powering of Tiny Devices Using Graphene Energy Harvesting

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Arkansas physicists have successfully developed a circuit capable of capturing graphene’s thermal motion and converting it into an electrical current. This lab curiousity only needs to be millions of times to power tiny low voltage computer chips.

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. The system seems to be energy harvesting from Brownian motion. The amount of graphene and processing needed to achieve this energy harvesting is system is something that can make sense for certain niches powering circuits but this is not something that would be practical for any large-scale energy generation. The “limitless” power refers to tiny, tiny constant trickles of power.

“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.

Fluctuation-induced current from freestanding graphene P. M. Thibado, P. Kumar, Surendra Singh, M. Ruiz-Garcia, A. Lasanta, and L. L. Bonilla Phys. Rev. E 102, 042101 – Published 2 October 2020

n the 1950s, physicist Léon Brillouin published a landmark paper refuting the idea that adding a single diode, a one-way electrical gate, to a circuit is the solution to harvesting energy from Brownian motion. Knowing this, Thibado’s group built their circuit with two diodes for converting AC into a direct current (DC). With the diodes in opposition allowing the current to flow both ways, they provide separate paths through the circuit, producing a pulsing DC current that performs work on a load resistor.

Additionally, they discovered that their design increased the amount of power delivered. “We also found that the on-off, switch-like behavior of the diodes actually amplifies the power delivered, rather than reducing it, as previously thought,” said Thibado. “The rate of change in resistance provided by the diodes adds an extra factor to the power.”

The team used a relatively new field of physics to prove the diodes increased the circuit’s power. “In proving this power enhancement, we drew from the emergent field of stochastic thermodynamics and extended the nearly century-old, celebrated theory of Nyquist,” said coauthor Pradeep Kumar, associate professor of physics and coauthor.

According to Kumar, the graphene and circuit share a symbiotic relationship. Though the thermal environment is performing work on the load resistor, the graphene and circuit are at the same temperature and heat does not flow between the two.

That’s an important distinction, said Thibado, because a temperature difference between the graphene and circuit, in a circuit producing power, would contradict the second law of thermodynamics. “This means that the second law of thermodynamics is not violated, nor is there any need to argue that ‘Maxwell’s Demon’ is separating hot and cold electrons,” Thibado said.

The team also discovered that the relatively slow motion of graphene induces current in the circuit at low frequencies, which is important from a technological perspective because electronics function more efficiently at lower frequencies.

SOURCES- University of Arkansas, Physical Review E
Written by Brian Wang, Nextbigfuture.com

19 thoughts on “Long term Powering of Tiny Devices Using Graphene Energy Harvesting”

  2. That seems more plausible. Ambient noise does actually feasibly serve as a source of energy, being organized movement, not totally random.

  4. This article was written about a paper from October 2020, and it sounds like they’re trying to extract energy from brownian motion, without a temperature gradient. That, of course, would be nonsense.

    But this paper from 2021 by the same group is clearer, and makes more sense:

    https://cpb-us-e1.wpmucdn.com/wordpressua.uark.edu/dist/3/316/files/2017/05/mdsim.pdf

    It says they’re harvesting energy from vibrations. So, presumably, it has nothing to do with Brownian motion. It’s just harvesting energy from small movements of the device and environmental vibrations. This would work on almost any moving vehicle, or something floating in the ocean, or even in a watch.

  6. This isn't clearly explained (at least to me). The most straightforward interpretation is that they're claiming to violate the laws of thermodynamics. I suspect that's not what they're actually claiming.

    More likely, they've built a way to extract energy from a thermal difference, or a thermal gradient. Which certainly could be used to power tiny devices. A device glued to your skin could be powered by the body warmth on one side and the colder air on the other side. But a device implanted in your body might not have access to a temperature difference, and so couldn't harvest any power.

    Or maybe they're confused, and actually think they've invented a perpetual motion machine. Who knows.

  7. According to the version of the story I read on another site, adding a capacitor is the next thing they want to try.

    And yeah, this one requires proof. Although they seem to be very transparent about how they did this, so it should be replicable.

  9. Wild guess here, perhaps they are letting the smallest Brownian jitters go by, but are looking at slower and bigger? motions that are also chaotic, but the result of many collisions, so it gets past the reversible "demon" state. Things slowly drift around with Brownian motion. If quant sez it will work, all bets are off!

  10. Did not read the paywall pub, but don't see the term "full . . ." anywhere. Is it actually mentioned? I was going by the description: "they provide separate paths through the circuit, producing a pulsing DC current that performs work on a load resistor" which seems to have done the task already. Do other parts act as diodes(rectifiers)? Out of my math depth with even the simple flow animation.

  11. Heat is, at the level of molecules and atoms, motion. In a solid, various sorts of vibrations. What we have here is basically, by mechanical analogy, a piston with a one-way ratchet pressing on a spring, in a box that's being shaken. Only the mechanical motion is converted to electricity by a capacitor one of whose plates is flexible; The capacitor is charged, and as the plate moves, its capacitance changes, so charge flows in and out, and the diode arrangement stores that.

    Now, in the macroscopic case this actually works, it's no different from those battery free flashlights that charge a capacitor by shaking them. At the microscopic level it doesn't work because Brownian motion is tiny, and requires tiny mechanisms, and the one way ratchet itself is being bounced around, and will release.

    Analogously, diodes have leakage currents, and that would discharge the capacitor just as fast as it charged at Brownian motion scale.

    The capacitor has to be charged for this to work; if it isn't charged, no current flows when the plate moves. Extracting the energy from the movement discharges the capacitor.

    I suspect what's happening is that they're just extracting the initial charge on the capacitor, and maybe the leakage current through the diode in the circuit that charged it from a battery, and that's why it seems to work.

  12. Well, no: As you can see, there were only two diodes, not four. Using a full wave bridge was just a proposed improvement.

  15. I am a bit confused. No thermal gradient but the thermal environment produces the work in the resistor? Ok, so the power (1/2 IR^2) comes from the Thermal bath. Basically a very efficient Peltier generator. I would guess that the generated power goes to near zero when the bath is near absolute zero Kelvin. So maybe useful when the thermal baths are very large & hot and your power draw is small. Or maybe I am very confused?

  17. I have to say that, as an engineer well versed in thermodynamics, I find it VERY hard to believe this can actually work. In theory, you could place this energy harvesting device in a closed box with an insulating partition, and direct the harvested energy to a resistor on the other side of the partition, and eventually a temperature difference would be created and sustained. Reduction of entropy in a closed system.

    So, based on principles so fundamental that it would completely overturn my understanding of the universe, I don't believe it.

    Second, notice the battery. If this is actually harvesting energy, why not another capacitor?

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