Implant Heat

Hello folks.  I've been mucking about with several ideas, but I keep coming back to the same issue: heat.  For the life of me I can't seem to find any data on the maximum threshold for the temperature increase from an implant before there is a risk of scalding.  Part of the problem is that it's on a sliding scale of time versus temp; knowing that a certain temperature is safe for up to 10 minutes doesn't help much with the logistics of a permanent implant.

So I guess the answer is simple: does anyone know of any research or documentation on this?


  • tape something to your arm at a variety of set temperatures and record your results lol
  • As a rule, if your implant is getting hot enough to be notices, it's not running efficiently and is not worth implanting. By the time you implant the thing you want it going precisely no higher than body temp.
  • I second chironex, anything over body heat should provoke an immune response over time. Thickening tissues, other fun stuff.
  • Your body does a really extensive job of trying to maintain a steady temperature inside. If you have something that disrupts that homeostasis, you are going to end up having a negative response.

    I guess the best response to your question is that you want an implant to be roughly around 37degC. If it's potentially going to scald, you are so far outside that window it's not even funny.
  • I would read the Cliff Notes on this study. Like Glims said, our body does an extensive job of maintaining body temperature. We're liquid cooled/heated. I imagine an implant location which gets a lot of blood flow, like the head, would have heat wicked away pretty quickly while an implant stuck in a fatty area with low blood flow, around the midsection, could build up some nasty heat.
    @OniExpress, maybe you will be the pioneer who finds out if we're a heat sink or an incubator.
    How efficient would it be to heat the body with implants which get power from inductive coils? Would too much energy be lost to transmission or could deep space pioneers be heated through sub-dermal coils? Or people who dive in cold waters?
    It would be so simple to put a enameled solenoid in silicone and place them along an arm or leg.
  • Incredibly inefficient. It would be better to wear a black suit and paint it with an infrared beam.

    Inductive chargers fall off with the square of the distance, so if you go past a few centimeters you've already lost a lot of power.

    Also as a note, inductive chargers would not work well at all in water. Water is a great absorber for radio signals, that's why we use SONAR on subs instead of RADAR.
  • @ElectricFeel, that was a vivid example, thank you.
  • ightden - Hah.  On a serious point, this would have a lot of complications.  To have the study be at all accurate, you would need to (a) maintain a steady test temperature (b) insulate the outside to the same level as human tissue.  It's not something I'm currenly looking into.

    chironex - I agree in general.  While I'm not looking into something running +15*F of the human body, I am curious if there's any knowledge of the effects of +1-5*F.

    ElectricFeel - Not "immune response" per say, but close enough.  This is the problem with temperature increase over time; I'm simply not aware of any data on the effects of even a +1*F change over a prolonged period.

    glims - Perhaps I shouldn't have used the phrase "scald".  I was referencing the only data I can seem to find, with is in regards to the temp/time scale as to when hot water will cause damage.  Something you're just fine with sticking your hand into for a minute will cause damage after 20 minutes.

    McSTUFF - Ironic that you mention inductive chargers, as these are one of the things that I was taking into consideration.  Induction charged batteries have the potential to get quite warm even without thermal runaway.

    ElectricFeel - Actually, depending on the distance from the induction source, you might be wrong.  Water is going to pretty much entirely block IR (though I haven't looked into the relevant ratios for induction dropoff), so you'd basically have an underwater space heater.  But yeah, water basically screws just any kind of high-energy transmission.

    Back to my original question, to be more specific what about the effects of an implant with an open-air temperature of +3*F of body temperature implant in a well-circulated area of the body (and ignoring any possibility of an uneven heat on one side or the other).  Are we looking at any immediate issues from a known experience basis, or are we having to use conjecture? 
  • About heating water. For cm distance and the rather low working frequencies of inductive systems we don't get that much water heating. So that part is cool unless you use GHz based systems.
    Biggest heat source are the losses of the battery (given you use a charger with high efficiency, but those are easy to get). Battery charge/discharge efficiency for Liion is bout 80-90%. The remaining 10 to 20% are lost in heat.
  • @Chironex what kind of heat losses do you see with graphene-based super caps?
  • No clue. Haven't made one yet. Been busy with vacuum and naoparticles. Although seemingly not very much. They're paper thin and can run for hours with no strain to the materials and the materials aren't particularly heat resistant so i can't imagine much. 
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