Internal heating and cooling

 @bsharbi gave me an idea after he posted this:
Used for heating or cooling some electronics devices.

Then I remembered this:

This device cools or heats you body by heating or cooling the blood in
your hands which then gets pumped to the rest of your body. The cooling
function greatly improves athletic performance. The power glove uses a
vacuum to bring blood vessels to the surface of the skin, which looks
dumb and renders one hand useless.

A subdermal device that uses micropelt wouldn't need a vacuum system,
since the device would be put right next to blood vessels anyway.


  • I think it's rather tricky to get an electrical cooling system to work inside the body.  Peltier elements are very inefficient; one side will get much hotter than the other side will get cold, and you will need a way to transfer all that extra heat out of your body (your body uses sweat, but it'd be difficult to sweat the right amount at a specific location).  A transdermal heatsink might be possible, but that doesn't seem like it's worth the effort.

    That said, I don't have a lot of experience with cooling systems, so take this with a grain of salt.
  • The electricity makes both hot & cold at the same time? I thought you needed to use two ingredients to make the third.
    cold+hot= electricity
    electricity+cold= hot
    electricity+hot= cold

    Is this a no? As far as efficiency, I think we only need a 4 degree temp variance to cool the body. There has to be a way around this.
  • In a motor, you put current in and get motion, or you put motion in and get current. Peltier devices work in much the same way. If there is a temperature difference between the two sides, you get current. If you put current in, you will get a temperature difference.

    In reply to the facebook discussion, here's something I sent to Brian earlier -

    I think it would work - even a small temp difference gives power. It's just a question of which technology gives you more power at a specific size - and what the minimum size is for each technology.
    Another thought i had for inductive energy transfer is to have a couple magnets to keep the coils aligned, so you could get max power transfer. Kinda stupid, cause you'd have to have some sort of mass energy storage on the implant, and you'd have to charge it often/ish, but it would allow you to implant a more active device
  • Peltier elements are heat pumps.  An electric voltage creates a temperature difference between the two sides of the element.  Since peltiers are usually less than 10% efficient, you create a lot more heat than cold.
  • It seems we are at an engineering roadblock for the cooling function. The heat function should be fairly easy though, right? What do you guys think? Resistor heating? What would be the best way to do that? 

    It would be cool to see if it could prevent hypothermia.
  • Resistive heating is easy, as you just have to run a current through an appropriately rated resistor.  A simple temperature controller is easy to build if you add in an op-amp (or microcontroller) and a thermistor or so.

    I'm a bit curious where you're going to get the energy from, though.  How many watts of heat did you intend on generating?
  • I think I just need a 4 degree increase in temperature (100-101 F?). I imagine I will have to use a battery. I have no idea how much power it would require. Say I wanted 6 hours @ 100 F. Does that require a car battery?
  • edited July 2012
    some basics: in order to cool down something, you need to transfer heat away from it. heat naturally transfers from hot to cold. if you want to transfer it the other way, you need additional energy (which usualy increases heat on the hot end)

    applied to a human body, you need do transfer heat out of the body. naturally this is done by either a cooler environment, or by evaporation of sweat.

    if you have a subdermal device, there is no way do transfer the heat away from the body because the only place to "pump" it is back into the body itself.
    so the only way to get anything done would be by having a transdermal device with a radiator to get rid of all the excess heat.

    and even if you'd go through all that trouble, it still requires a lot of energy to actually operate such a device. energy you either have to supply externally.

    the only way that's somewhat imagineable is by implanting a container with a chilled liquid/gas, and have it exchange heat wtih your body at defined rates on demand. but that'd have more disadvantages than putting some icecubes in a towel and putting it around your neck.

    about heating. your body would try to counter-act against any increase in temperature that's not healthy. if you want to increase your body temperature by 4 degrees fahrenheit (i'd ask you to use centigrade in future), that'd make 2 degrees celsius. for a 80kg body makes 160000gK*4,2J/gK makes bout 670kJ of energy. for the initial heating. That's about 180Wh of energy which equals to a 12V battery with 16.6Ah capacity, which would be a car battery with roughly 6kg of weight. and that's without your body doing anything against that additional heating.

    so. long story short. putting a wet towel in your neck does a great job for cooling, wearing an extra layer of clothing for heating. technical (especially electrical) sollutions are not suited for mobile or longterm use. and implanted devices are pretty much out of question.
  • I'm no wizard, but is that a fair way to determine our heating requirements? We are heating blood in one spot to deliver warmer blood to the rest of the body. I think blood pumps through the body every 30 seconds or so. Do we need to have those power requirements since we aren't heating the entire mass?

    Maybe resistive heating isn't the way to go? There are a lot of cordless heating pads on the market. These things use flir
    Would that be better? It probably wouldn't last as long as I'd like it to, but it would be a start.
  • from what i read from your comments you wanted to raise the body temperature by 2 degrees. for me, the body counts as an object of about 80kg of mass mainly made from water.

    my calculation was the absolute minimum value (assuming the body does _nothing_ to get the temperature down to normal and perfect thermal insulation)
    if you use resistors for heating you'll get a 100% heating efficiency. you can expect the actual energy requirement to be a much higher than my physically idealistic number. besides, vaporative cooling (aka sweating) is extremly effective.

    the product you linked only heats a spot to treat injuries. heating a few cubic centimeters of skin and muscle is not the same as heating 80kg of body mass.
    besides that. heating only a part of your body is easily tollerated by the body itself as it hardly affects overall temperature.

    heating the body would be pretty much like artificial fever. i don't see what good it would to except causing major discomfort.
  • The goal isn't to induce an artificial fever, obviously. The heating function is like a radiant floor heating system. It would only be used to stabilize temperatures in very cold conditions. Might be handy for a navy frogman in freezing waters.

    Has anyone here had an IV with some cool plasma or saline? You get a sudden chill that spreads through your body very quickly. The temp difference is only slight, but it can cause you to shiver like mad (15-20 minutes for 1 bag and then it lasts another 10-15 minutes after the drip is finished). The cool saline is only being applied in one vein usually. A warm bag of saline should have the opposite effect I imagine. Hell, people soak their feet in warm water and get similar whole-body warming effects too. Anyway, the power glove guy in the above video claims it works.

    I guess I could do some experiments. 
  • All I can say is that it's almost certainly not going to happen without a relatively free transfer from inside <-> outside the body, and even that is going to be pretty difficult.
  • Not quite. I was actually discussing that article with somebody recently; the device doesn't actually cause any significant change in body temp, but rather uses the body's natural tendency to acclimatize to "trick" your brain into thinking you're cooler/warmer.
  • So, it manipulates the body's systems to change your actual temperature? Or does it simply change your perception of the temperature?
  • The latter. If there is any overall change in body temp it's negligible.
  • interesting. The powerglove device causes a legit change in temp though. That MIT wrist device could probably work for heat. I did a heating experiment with a heating pad strapped around my bicep while in an ice bath (15 min off/15 min on, temp taken continuously) and that kept my body temperature in the normal range.
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