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Power Hardware

Microchip Powered by Body Heat 73

Posted by CmdrTaco
from the i-couldn't-power-an-8088 dept.
An anonymous reader writes "MIT and Texas Instruments researchers have designed a chip that they say could be up to 10 times more energy efficient than current technology. The chip's power consumption is so low that devices with the chip may even be able to be recharged using the owner's body heat." The intent is to use these in medical applications like pacemakers where one would expect to have the free power source.
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Microchip Powered by Body Heat

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  • Powered by heat? (Score:4, Interesting)

    by Bazman (4849) on Saturday March 22, 2008 @08:55AM (#22828632) Journal
    Two things spring to mind:

      1. If it's powered by your body heat, it's going to make you colder...

      2. Don't you need a temperature _gradient_ to get useful power out of heat?

    • I imagine heart muscle temperature is higher than blood temperature.
    • Re: (Score:3, Informative)

      by masshuu (1260516)
      answer to number 1: No, about 60-70% of the energy we produce is heat energy. Much of it is excess that is lost through the skin. A small chip that doesn't need much power won't steal your body heat and make you cold.
    • Re: (Score:3, Interesting)

      by EaglemanBSA (950534)
      1.) Yes, it will indeed take heat from your body, but it would do nothing more than force the heart to pump a little more blood to maintain your body temperature. Many people don't know that one of the many functions your cardiovascular system performs is temperature control - it's one of the world's most complex heat exchangers. You introduce a small enough cold sink, and it will heat that area of the body up to make up for it. 2.) That depends on how they're getting power from the heat - if it's powering
      • by norton_I (64015)

        (e.g.: when using two dissimilar metals to generate a charge, the absolute temperature is directly proportional to the reaction rate).


        Thermopower from bimetalic contacts definitely requires a cold junction to generate power.

        If you are talking about a consumable chemical reaction, then all you have is a battery. It is true that chemical reactions often go faster at elevated temperatures, but that is not the same thing.
        • At super low power/voltage it may be possible to rectify thermal noise in a warm semiconductor and use it to power circuitry. There are probably other ways to harness heat without a thermal gradient too, heat is just motion at an atomic scale so if you can harness that motion for power you don't need a gradient, just like a windmill doesn't need a wind gradient to work. It would convert heat to energy and thus cool itself, but the human body produces about 100W and a medical device would use a small fract
          • by norton_I (64015)
            Uh, no. You can't rectify thermal noise, at least not on a continuous basis. Thermal noise has zero power content -- that is what thermal noise means. The force is 90 degrees out of phase with the displacement so the average power is zero.

            A wind turbine requires a temperature gradient to operate, which is what generates wind in the first place.

            Please see the second law of thermodynamics, the first law of thermodynamics, and Maxwell's demon.
      • by internic (453511)

        That depends on how they're getting power from the heat - if it's powering a heat engine and runs off heat flux, then yes, they would need a temperature gradient (which isn't that hard to get anyhow - put the cold sink near the epidermis and the hot sink near your heart/brain/etc.). If they're using the heat to run a small chemical reaction, then no, they probably wouldn't need a temperature gradient (e.g.: when using two dissimilar metals to generate a charge, the absolute temperature is directly proportio

    • In the current Dutch issue of "Scientific American," there's an article about body microgeneration.

      One proposal is to use microscopic plates separated by orthogonally arranged nanotubes. Connected to one plate and touching small feelers on the other, they would function as a piezoelectric generator for exploiting ambient motion. The idea is to apply this to similar applications as in TFA.

      As far as using body heat as an RTG [wikipedia.org], the idea is of course to use the temperature gradient between the body and the amb
      • by Nairanvac (912343)
        The Dutch Scientific American? Wouldn't that just be the Scientific Dutchman?
        • by Dr. Cody (554864)
          Yeah, I know. When I saw it at the newsstand on vacation, I did a double-take and got a copy. The front page says "Scientific American - Nederlandstalig" ('in Dutch').
    • Your first point is wrong; our understanding of thermodynamics doesn't let us make heat simply go away, because your second point is true. This chip would have to use a thermocouple and extract energy from the *flow* of heat. Which, I wouldn't expect there to be much of a gradient inside the body...
    • by MrNaz (730548) on Saturday March 22, 2008 @09:53AM (#22828888) Homepage
      1. Having skin exposed to anything less than 37oC makes you colder. Losing a few extra W of thermal energy to power a microchip will not make a difference, it's trivial compared to the amount of energy you lose just by being exposed to air.
      2. No, chemical reactions that are endothermic will occur at any temperature that supplies the necessary activation energy to the physical reagents.

      Hope I didn't sound like an elitist snob...
      • by Fëanáro (130986)

        2. No, chemical reactions that are endothermic will occur at any temperature that supplies the necessary activation energy to the physical reagents.

        But unless you have a source of new reactants, and a place to dump your product, your reaction will soon reach chemical equilibrum.
        Essentially that is a battery.

        You really need some sort temperature gradient to convert body temperature into work. I do not see how a device inside the body could do that with any efficiency.

        • by MrNaz (730548)

          unless you have a source of new reactants, and a place to dump your product

          What, you mean like the bloodstream, which supplied readily combustible sugar and carries away the products of glucose reactions?

          • by Fëanáro (130986)
            If you are using sugars from the blood as a power source (possible, but I think beyond current technology) then you are definitely not recharging by "using the owner's body heat", which was the point of this thread.
            • Good pun...

              But actually, I don't see why someone hasn't developed an ATP (?) powered circuit! All you need is a cathode with an enzyme or catalyst that breaks apart sugars and steals their electrons, and any kind of anode. Given the current state of molecular engineering - and certainly cell tinkering - this should be almost easy!

              Obviously this has already been buried by Big Oil, along with the Free Energy device, test-tube Cold Fusion, and the Perpetual Stirling Engine.
              • by Fëanáro (130986)
                I do not think you would find ATP outside of a cell. IIRC ATP acts as a pain signal if found outside of cells, since that would indicate some ruptured membranes.
                So this bot would have to drill into fresh cells and suck them out.

                If it was not for the pain thing, and the difficulty in getting it into cells, I would market an ATP energy drink.
                Guaranted to give you back energy instantly, whitout any sugars and fats!
      • >1. Having skin exposed to anything less than 37oC makes you colder. I think this is wrong. Having skin exposed at 37C would make you very hot. Your body produces excess heat that has to be expelled somehow. At 37 the environment wouldn't take any heat away from you so your body would start to sweat in an effort to get rid of the excess heat more efficiently.
        • by MrNaz (730548)
          "I think this is wrong."
          Then you think wrong. How you "feel" about the temperature is not relevant to the actual temperature. Furthermore, my point was that the body generates huge amounts of heat, the use of which will not affect the body adversely.
    • by vertinox (846076)
      1. If it's powered by your body heat, it's going to make you colder...

      Considering how much of your body is devoted to getting rid of excess heat (skin and sweat glands) I don't see this as a bad thing.

      2. Don't you need a temperature _gradient_ to get useful power out of heat?

      It never hurts to exercise.
    • by mikael (484)
      1. If it's powered by your body heat, it's going to make you colder...

      If you turn down the thermostat on your central heating it's going to make you colder... ... but your body will burn more calories to maintain core and extremity body temperature.

    • 2. Don't you need a temperature _gradient_ to get useful power out of heat?
      My physics is a bit rusty, but I could swear that generating power without a significant gradient violates the 2nd law of thermodynamics. OTOH, if they've figured this out, maybe we will have yet another patent in the works for a perpetual motion machine.
      • by Pyrrus (97830)
        It depends what you consider significant. According to Carnot's theorem, the efficiency of a heat engine is increases with the difference between the hot reservoir and the cold reservoir. So the difference between one's body temperature and ambient temperature isn't much, therefore efficiency is low, but power can still be produced.
        • That would work for a chip mounted somewhere on your body (as long as you stay someplace cold; no summer trips anywhere tropical for people that would depend on this), but for devices implanted in your body, like a pacemaker, wouldn't this still be a problem?
    • by chanio (321367)
      They surely got inspired with the animated film Matrix Renaisance. At least, there is now a reason to keep most of our race alive...
  • The article mentions implantable devices running off body heat - how would that work? I thought to harvest energy you needed a temperature difference, where would an implanted device get that?

    Just wondering...
    • by protobion (870000)
      The normal "core" body temperature is 37 deg C. Skin however, being exposed , is substantially cooler at 30 deg C when bare and exposed to ambient temperature. A 7 deg difference has been harvested for energy before using Low temperature differential sterling engines.

  • by Timesprout (579035) on Saturday March 22, 2008 @08:57AM (#22828644)
    you insensitive clod!
    • by lyml (1200795)
      It's cool, it works with difference in temperatures.

      Oh wait cool, sorry about that didn't mean to be all cold.

      Oh wait cold... I'll just shut up now...
  • Dupe! (Score:5, Informative)

    by Clazzy (958719) on Saturday March 22, 2008 @08:57AM (#22828650)
    We [slashdot.org] know [slashdot.org]. It did seem like a familiar read.
  • by hyades1 (1149581) <hyades1@hotmail.com> on Saturday March 22, 2008 @09:03AM (#22828674)

    "The chip's power consumption is so low that devices with the chip may even be able to be recharged using the owner's body heat."

    Except, probably, my ex. She'd have to to crawl up onto a rock and bask for a couple of hours before something like that would work for her.

  • by constantnormal (512494) on Saturday March 22, 2008 @09:34AM (#22828810)
    ... would seem to be a much more likely implanted medical device than pacemakers to use this technology. Having a pair of fully-implanted, self-powered devices that independently provide sound to each ear would seem to be a huge step forward, and readily achievable with this sort of technology.

    And with a generation rapidly driving themselves deaf via iPods, a technological solution like this would seem to be appropriate and is arriving just in time.

    While I don't know what kind of voltages and currents a pacemaker uses to regulate heart activity, it would seem a lot more likely that a cochlear implant would use less. Plus, there's a lot less downside risk if the device malfunctions.
    • by ruinevil (852677)

      Plus, there's a lot less downside risk if the device malfunctions.


      Until the device (probably the battery) explodes in your skull.
      • Re: (Score:3, Funny)

        by gomiam (587421)
        Until the device (probably the battery) explodes in your skull.

        ... and its residue mixes with your brain (whatever was left) and makes you search for spare parts (braaaaiiiiinnnnssss...).

    • Re: (Score:3, Interesting)

      by InterGuru (50986)
      I have a pacemaker. The manufacturer ( St. Jude ) claims that the battery will last 6-8 years.

      In the old days pacemakers used a plutonium powered thermoelectric battery. This lasted forever, or about 25,000 years to be precise. They are now banned in the US because of the danger that the plutonium could be released in some way, such as a plane crash, a gunshot wound, or crematorium . They actually had to dig up some bodies because the undertaker did not remove the battery.
  • by Snarkhunter (1056150) on Saturday March 22, 2008 @09:35AM (#22828820)
    I think we have. Except that in the movies, the humans weren't dumb enough to TEACH the robots to feed of body heat. Oh well. I for one would like to offer our slightly peckish robotic overlords a light brunch.
    • I think we have. Except that in the movies, the humans weren't dumb enough to TEACH the robots to feed of body heat. Oh well. I for one would like to offer our slightly peckish robotic overlords a light brunch.

      Right, but unlike in that movie we have the laws of thermodynamics to protect us.

      I love The Matrix, but science was not its strong point.

  • I suppose that a heart attack would be a better way to go than freezing to death.
  • Throughout human history, we have been dependent on machines to survive. Fate it seems is not without a sense of irony. The human body generates more bio-electricity than a 120-volt battery and over 25,000 BTU's of body heat. Combined with a form of fusion the machines have found all the energy they would ever need. There are fields, endless fields, where human beings are no longer born, we are grown. For the longest time I wouldn't believe it, and then I saw the fields with my own eyes. Watch them liquefy
  • Isn't this the third time we see this? [1] [slashdot.org] [2] [slashdot.org]
  • This is just one step closer to harnessing the incredible power generated by the hands (or finger, I guess... if that's your thing) of over-stimulated teenagers. I, for one, welcome our sticky overlords... I just won't shake their hands.
  • Need to up the voltage to speed that pacemaker up? No problem, just get the flu.
  • by Katatsumuri (1137173) on Saturday March 22, 2008 @11:40AM (#22829538)

    This research has been covered at least twice on Slashdot recently:

    Researchers Design Microchip Ten Times More Efficient [slashdot.org]

    Low Voltage Is Key To Energy-Efficient Chip [slashdot.org]

    Maybe those should be included as related articles in the summary, or something...

  • Now geeks will have an excuse to snuggle up to other people...
  • I wish reporters had to take a class in basic science.

    You can't effectively harvest body heat. The efficiency of any heat engine is proportional to the temperature drop, in absolute degrees. The internal body temperature gradient is unlikely to be much more than a degree Farenheit. So any heat engine in the body is limited to an absolute best efficiency of under a quarter of a percent. And you'd have to find some working fluid that changes phase across that temperature range. Not very likely. You co

    • by VanessaE (970834)
      Who's to say that one couldn't design a large version of this chip (or something remotely similar), and implant it just under the skin? You'd want to put it somewhere on/in the patient's upper back, neck, just under the scalp, or anywhere else that is naturally warm and at the same time, usually exposed to the ambient air. Seems to me that would be the easiest way to get a fairly large gradient, especially on a cool day.

      The same should hold true for the lower legs - the body surely has to expend at lea

      • Okay, let's do the math. The human body dissipates about 150 watts through a surface area of around two square yards. That's about 2600 square inches. Let's say you used a 5x5 inch patch. That's 25 square inches, about 1% of the body surface. So you could at best capture 1% of 150, or 1.5 watts of heat. The heat to electricity efficiency of a typical thermocouple is about 3%. So we might get 45 milliwatts of electricity. Maybe enough to power a watch or calculator or very slow (5 MHz) computer. By

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