Graphene Generates A Little Power

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.

44 thoughts on “Graphene Generates A Little Power

    1. Yeah. Measuring noise and poorly averaging it maybe. Any power generation is probably just an artifact of excessively sensitive instrumentation and imperfect averaging. And lack of rigor. Feels like another emdrive.

      Extracting work from Brownian motion? Alright fine, but we’re gonna need a HELL of a lot of good evidence and independent verification. But ofc science journalism reports on it breathlessly and deceptively right away. We really need to do something about that. There’s no science with this kind of pseudo-clergy thing going on, it ruins the whole process.

      1. I’m similarly skeptical. To cure the sensationalism, we need to look at the cause. Typically, funding for projects is authorized by some entity that drives these pitches by falling for them. Some organization somewhere wants to see this kind of headline braggadocio for some reason. Probably a university president looking for name recognition.
        Another idea is that the publication is looking for clicks and producing clickbait to shore up some budget.
        I’d like to see research like this become some kind of almost
        unconditional employment. Education and research assistance for healthcare and a livable wage, to replace the majority of welfare payouts. Participants would get credentialed over time and be more employable. Just some thoughts I’ve been brewing.

        1. The carrot in this project is potential for construction via photolithography or similar processes which may have the potential to scale the effect demonstrated (proposed?) up to some meaningful microwatts of power, the kind of thing that could be a couple of dozen layers thick on the inside of a medical implant and potentially power the implant. I’m not sure why the claim to be harvesting Brownian motion got glommed onto the whole thing, maybe for attention, but there are plenty of environments (inside the human body, on a highway overpass, on a ship car or airplane) which have a lot of vibrational energy to harvest.

    1. Nah. A crystal radio obeys entropy. This apparently extracts power from waste heat. Be extremely skeptical. Or maybe there’s some better explanation hidden in there going over my head, who knows. But this smells funny to me.

  1. After all is said and done more was said than done?
    I suggest the people need to consider what Mark mentioned stray electric fields and a diode “generate” electricity in small amounts (part of how an AM radio functions at least).
    I didn’t see a paper referenced regarding it.
    However an interesting possibility would be to use the semiconductor behavior of graphene with efficient antennae to make a wireless power transmission system. At least they didn’t use the words Novel and or Magic (humor mostly).

  2. Those who think diodes can act as one-way ratchets to extract energy from Brownian motion would do well to read and/or watch Feynman’s lectures where he discusses Brownian ratchets and pawls.

    Many smart people have fallen into those traps, and I suspect many will continue to repeat the mistakes of those who fell before them.

    Something about those who fail to study history…

      1. me too, once there was this literature class, it was boring as hell, so i took my notebook and started to work on some assembly program for a pc demo program, it was very hard, so i needed to concentrate more, then all of a sudden the teacher-boy stepped to my desk and grabbed my notebook, stating that i must write some love-letter :) and to his surprise, when he was unable to understand the pc’s assembly syntax, he asked me what the hell is it, then i told him that this is an important routine for my next demo program, all of the students, who knew me well, started to laugh, the teacher’s head get very red, very quickly :) as for the footnote, it seems that this stupid teacher was humiliated very well, because he took his revenge on me: he talked with other teachers and forced me to repeat the year…

  3. Good luck getting energy out of this system with real life components. Diodes have voltage drops, reverse leakage currents etc. Schottky diodes may have lower but still significant drops and high leakage vs silicon high drops and low leakage.
    e.g. silicon switching diode like BAV99 has 30nA of leakage which already higher than the 20pA mentioned.

    Also lossy capacitor etc.

    1. This comperision with a BAV99 is bs. On chip level 30nA are enough for an entire ultra low power circuit. Of course 20pA is way less… but still: a great effort of this research team!

      1. Talk is cheap. Care to name a common diode that has lower than 20nA leakage current and yet low enough drip off? Have to base the comment on a rel life part aka ”banana for scale”. If there is no diode that can work, then this is just fantasy.

        What’s your problem anyway?

      2. There might be no actual real life diode that would work.

        If the bandgap for the diode is too low, then a small amount of thermal energy would be enough for an electron to overcome. (i.e. leakage). Since this is essentially those random thermal energy, there is the big leakage problem there. There might be no practical way of actual implementation.

        If the bandgap is high enough to prevent leakage due to random thermal fluctuations, then most if not all of the voltage is lost at the forward dropout. It work work with a passive charge pumps.

        At the end of the day, it is worse than the usual snake oil free energy BS.

  4. The notion that it should be impossible to do this always troubled me. We extract energy from chaotic motion on a bigger scale, eg the snake shaped electric generators that float in the sea. I always wondered, as you scale that down, in a thought experiment, at what point does it become impossible, and why.

    1. What will really get you.
      At what point do you reach the limit to power density, essentially the equivalent, inverse moor’s law, as it where. Where you struggle to get potential kinetic energy into the system.

    2. Extracting energy out of random motion is a system that’s described by the thought experiment of the Maxwell’s Demon. It’s a demon that seems to create a temperature difference (potential energy) out of nowhere by opening and closing a door to pass high energy gas molecules into a container and leaving the low energy molecules out as they bounce around randomly.

      The trick is: “it would take more thermodynamic work to gauge the speed of the molecules and selectively allow them to pass through the opening between A and B than the amount of energy gained by the difference of temperature caused by doing so.”

      That’s basically the point against generators trying to harness Brownian motion. Trying to extract energy from random fluctuations inside an equilibrium system doesn’t work because it takes just as much energy to do so. Wind power and waves on the sea aren’t like this – they are not at a thermal equilibrium since the energy is trying to flow somewhere with lower potential (ultimately to radiate out into space), so we can catch it along the way.

  5. “clean, limitless power”, why does that sounds like a perpetual motion machine.

    If they are extracting electrical energy from brownian motion within graphene at thermal equilibrium, does the system cool ?

    1. The summary of the actual paper appears to acknowledge that no energy can be extracted if the temperature of the whole system is the same.

      “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. However, there is power dissipated by the load resistor, and its time average is exactly equal to the power supplied by the thermal bath.”

      So it sounds like their plan would be to use this to extract energy from temperature differences.

      1. Damn I hate paywalls! Thanks for that quote though. It sounded like that to me. I’m also a little concerned over the use of Brownian motion to describe the fluctuations. These are atoms bonded in an aromatic molecule. Fluctuations in the curvature of polyaromatics is known to have very odd effects. I have long since lost the link to the paper I published on 3rd order hyperpolarizability related to curvature of aromatic polycyclics (back in the mid 90s). (p.s. by curvature I mean non-planarity, but including things like bucky-balls)

  6. Is this a sort of AC FET? That probe is creating a field. They show the effect is related to field, but obviously there is no current source outside the experiment, so a FET/battery mishmash? I’m lost in electronics that do not plug and program, as you can see.

  7. The animation shows how a energy pump and voltage multiplier is used to harvest that little power.
    For more info about this (from 2017) A Potential Source of Clean, Limitless Energy

    From a comment by “Junker Zn 2 years ago”

    There’s nothing special about this. It isn’t a perpetual motion machine or battery. It simply harvests a small amount of energy from thermal and vibrational variations of the surrounding environment that are big enough to harvest. There are many devices that can do this by various means. Small amounts of energy can be harvested from wifi signals, for example. None of these devices produce very much energy and none of them can be scaled up because the amount of energy available to harvest is tiny and not really based on receptor volume. The energy involved here is not coming from the quantum vacuum, but travels to the receptor through the air (like a wave), so the amount you can harvest is more a function of an intersection from the source and not a function of volume. In fact, simple pendulum winders found in watches that harvest a little bit of energy from your normal arm motion generate far, far more energy than this device ever could.

    In this particular case, the more charge associated with the sheet of graphene, the less mobility it will have. To act as a battery the graphene needs to be able to pump charge, which basically means bringing together objects with the same charge. That requires something doing work… the work is harvested from the environment, but the environment must contain sufficient differentials in what is being harvested to generate enough of a voltage differential to be useful and that’s really the limiting factor here.

  8. wonder if this is related to lattice confined fusion:

    there they write “A novel feature of the new process is the critical role played by metal lattice electrons whose negative charges help “screen” the positively charged deuterons”

    to me this help to “screen” seems to be assisted by thermal fluctuation ot the lattice and the electrons, but its just an wild guess.

  9. Graphine is also the correct scale to turn light into current, if you could get a high speed diode then you could do Direct EMF conversion from sunlight into electricity at nearly 100% efficiency.

  10. I live on battery technology. Everything on this subject is of primary interest because of its importance to us, living off grid with no access to ANY utilities. I am still staying with flooded lead-acid batteries for now for several reasons and am at end-of-life for the current(;-)) bank until I can get a new matched set of Trojan L16s.

    I have seen several articles and have concluded this to be current day hype. It will be MANY years in the future before this has a commercial application and even then it will be very low draw, efficient electronics. Sigh. I was initially excited that there could be a way to use nuke waste products and product non-recharged batteries at the same time.

    But I also sense a patent battle in this technology. Dang, the lawyers will do what they do….

    1. For nuke power lookup beta batteries. They have been around forever at low outputs, some recent press about diamond nuke batteries scaling up to higher outputs, but far from commercialization.

  11. The measurements were made in a STM under ultra-high vacuum. STMs usually are measuring the number of electrons that tunnel to a probe nm away from a conductive sample piece, so they are well shielded to see such small currents.

  12. This isn’t harvesting Brownian motion. The novel attribute here is that graphene is a 2D sheet and is converting Brownian thermal motion into surface ripples in the sheet of graphene. These sheet waves are coupled to a nearby STM probe.

  13. Makes sense, thanks.

    Still this residual creepiness of statistical mechanics lurks, like those monsters beneath the bed. When you switch on the lights, they’re gone, but when it’s dark… :)

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