5 ms·

Title is very unclear, but it looks like they're modulating thermal conductivity with an electric field. It's definitely not a peltier junction as I thought at

Title is very unclear, but it looks like they're modulating thermal conductivity with an electric field. It's definitely not a peltier junction as I thought at first. Seems like this is actually a novel mechanism. Very interesting, I wonder what applications it will find? Cooling of CPUs seems like a bad use case, but I'm sure someone will find a very interesting application

dragontamer 3y ago
I agree. Cooling of CPUs is awful use of this tech. Why would anyone turn down thermal conductivity? Just always be sucking heat out. -------- The most obvious application would be electrically controlled insulators. If it's winter or summer, insulate the house. But if outdoors is 72F (or 21C or another ideal temperature), let the ideal temperature into the house. Temperature controlled crystal oscillators are another application IMO. Applications where we have a 'target temperature', and easy access to differing temperatures (ex inside the oven vs outside the oven vs the heat from a heater)
- andbberger 3y ago
  modern houses should be well-insulated, using heat exchange ventilators and heat pumps get proportionately more efficient in these conditions. i will be shocked if this is ever viable economically.
  - Retric 3y ago
    One possibility you lose from a well insulated house is the heat collection potential of your roof on a cold day. The roof is receiving close to 1,000w/m2 and that energy is just wasted. Passive houses use a lot of tricks around the angles light enters a home and skylights etc to collect that energy, but a system that uses little energy and doesn’t have moving parts so it can last the lifetime of the home should allow for more options and thus lower costs. PS: Solar thermal systems work well and have a fairly short payback period, but involve both moving parts and fluids.
- LoganDark 3y ago
  > Why would anyone turn down thermal conductivity? Why do you think CPU dies can still only be cooled directly over the parts that are generating heat? If I read the article correctly, this tech isn't just the ability to turn off thermal conductivity that already existed, it's the ability to add thermal conductivity that you couldn't before.
  - dragontamer 3y ago
    We already have high-quality thermal conductors and its name is copper. And copper runs throughout the inside of all of our chips. I have severe doubts that any "heat semiconductor" would have the same thermal-conductance as copper (or copper heatpipes, and other such heat-devices we have today).
    - LoganDark 3y ago
      But copper is conductive, so it will conduct electricity too. This could possibly be placed in areas where copper can't be, maybe even much closer to (or even directly contacting) the actual copper traces in the chip. Unfortunately I don't know enough about CPU manufacturing to speculate much more than that.
      - dragontamer 3y ago
        You're asking for a thermal jumper. I don't know much about the inside of CPUs either. But I know that at the PCB-level, we use these devices to carry heat but not electricity. https://www.vishay.com/en/product/60157/ https://www.vishay.com/en/product/60157/ Copper is still better at conducting heat. But just a little bit of thermal-jumper to make that small electrical separation is all you need. Datasheet: https://www.vishay.com/docs/60157/thjp.pdf https://www.vishay.com/docs/60157/thjp.pdf In any case, modern material science provides us with plenty of useful insulators, conductors, thermal-conductors (but not electrical), semiconductors, and now semi-heat conductors (erm, thermal semiconductor?) I don't expect the thermal semiconductor to be replacing any of the other materials we already use. Instead, we will find new discoveries and applications for things I can barely imagine.
- mitthrowaway2 3y ago
  Perhaps another application is insulation of batteries. You want good thermal conductivity when the battery is in active use at high power draw to sink heat to the environment, but also you may want to insulate it when it's idle and freezing outside, to reduce how much self-discharge is needed to maintain its minimum temperature. However, it might be simpler to do this with moving parts or phase-change materials, etc
- c22 3y ago
  You could switch the thermal sink between multiple radiators to give each one a lower duty cycle.
  - dragontamer 3y ago
    Heat naturally flows to the lowest temperature object connected by the lowest thermal-resistance (or highest thermal conductivity). If you have a radiator at 80C, and a 2nd radiator at 60C and both are connected to HotPlate-X, the heat will naturally find itself going to the 60C, while the 80C will more naturally find its own heat radiating out to the environment quicker. You don't need a thermal-semiconductor to just have heat flow around. That's just... heat physics. -------- There seems to be some practical applications for this new "thermal semiconductor". Though the next questions are that of cost, performance, etc. etc.
    - jfoutz 3y ago
      it (the insulator) seems very small. I think, a lot of chips have multiple temperature sensors across the whole chip to decide when to clock down. If I have 4 cores, and 1 is going flat out, I could see insulating the unused (or lesser used) cores. The idea being give the hot part the full cooling capacity. That seems like the obvious idea. But maybe I'm misunderstanding or forgetting something fundamental.
      - LoganDark 3y ago
        > The idea being give the hot part the full cooling capacity. Isn't it also to prevent the hot part from heating the other, cooler parts? This could be used to give each part of a CPU its own independent cooling. That'd be pretty cool.
      - yetihehe 3y ago
        You can use this to equalize temperatures on one chip, using it like a changeable heat-shield, so instead of hotspots, you artifically keep some heat from escaping from colder areas too fast which could prevent stress induced cracking. It's better to keep whole chip at 70*C than a one small area at 70 and other areas at 30. Then when heat load from that one small spot vanishes or is moved to other spot, you can change your heat mask on the fly.
- amelius 3y ago
  > Cooling of CPUs is awful use of this tech. Why would anyone turn down thermal conductivity? Well, you could build logic gates out of these switching elements ;)
Terr_ 3y ago
> I wonder what applications it will find? New analogies for Maxwell's Demon. :p This out of left-field, are there any military applications in when it comes to vehicles' appearance in thermal imagery? I suppose you wouldn't need something like this for the relatively slow switching of stuff like "which side of the tank should be the hot side".
- yetihehe 3y ago
  > are there any military applications in when it comes to vehicles' appearance in thermal imagery? Yeah, you can now display moving images for thermal imagers, like showing the temperature of terrain behind vehicle while moving around.
  - Terr_ 3y ago
    It sounds like that depends on having outer tiles with basically no heat capacity so that each cools instantly... Or else something ready to pump the heat away.
    - yetihehe 3y ago
      Yeah, like a thermal transistor. When temperature transfer is blocked, outer surface of that transistor should pretty fast go to ambient air especially with moving air. Remember that transistor is only several atoms thick and can switch at megahertz speeds.
Sanzig 3y ago
Definitely would be really interesting for spacecraft thermal management. Spacecraft only have radiation as a heat transfer mechanism, and they need to be designed to keep all components within a safe temperature under a range of operating conditions (eg: from receiving no sun on the dark side of a planet to full sun a few minutes later). A satellite in low earth orbit can experience a dozen or more sun/eclipse cycles per day, which makes thermal cycling a major factor in long-term reliability. Moving parts are strongly discouraged for reliability reasons, so thermal design needs to be as passive as possible. Having a solid state switched thermal conductance path would be a huge benefit. Imagine being able to switch a radiator off in eclipse to conserve heat and on in sun to reject it.
__MatrixMan__ 3y ago
A device that makes jesus toast (other images too I guess).
jjk166 3y ago
I would think the ideal use case would be for scientific equipment where a very precise temperature needs to be maintained. Right now you either have a large thermal mass to prevent fluctuations (which also means you can't quickly and precisely vary the temperature), or you just accept the thermal noise and try to compensate for it in the analysis.

dragontamer 3y ago

I agree. Cooling of CPUs is awful use of this tech. Why would anyone turn down thermal conductivity? Just always be sucking heat out. -------- The most obvious application would be electrically controlled insulators. If it's winter or summer, insulate the house. But if outdoors is 72F (or 21C or another ideal temperature), let the ideal temperature into the house. Temperature controlled crystal oscillators are another application IMO. Applications where we have a 'target temperature', and easy access to differing temperatures (ex inside the oven vs outside the oven vs the heat from a heater)

andbberger 3y ago
modern houses should be well-insulated, using heat exchange ventilators and heat pumps get proportionately more efficient in these conditions. i will be shocked if this is ever viable economically.
- Retric 3y ago
  One possibility you lose from a well insulated house is the heat collection potential of your roof on a cold day. The roof is receiving close to 1,000w/m2 and that energy is just wasted. Passive houses use a lot of tricks around the angles light enters a home and skylights etc to collect that energy, but a system that uses little energy and doesn’t have moving parts so it can last the lifetime of the home should allow for more options and thus lower costs. PS: Solar thermal systems work well and have a fairly short payback period, but involve both moving parts and fluids.
LoganDark 3y ago
> Why would anyone turn down thermal conductivity? Why do you think CPU dies can still only be cooled directly over the parts that are generating heat? If I read the article correctly, this tech isn't just the ability to turn off thermal conductivity that already existed, it's the ability to add thermal conductivity that you couldn't before.
- dragontamer 3y ago
  We already have high-quality thermal conductors and its name is copper. And copper runs throughout the inside of all of our chips. I have severe doubts that any "heat semiconductor" would have the same thermal-conductance as copper (or copper heatpipes, and other such heat-devices we have today).
  - LoganDark 3y ago
    But copper is conductive, so it will conduct electricity too. This could possibly be placed in areas where copper can't be, maybe even much closer to (or even directly contacting) the actual copper traces in the chip. Unfortunately I don't know enough about CPU manufacturing to speculate much more than that.
    - dragontamer 3y ago
      You're asking for a thermal jumper. I don't know much about the inside of CPUs either. But I know that at the PCB-level, we use these devices to carry heat but not electricity. https://www.vishay.com/en/product/60157/ https://www.vishay.com/en/product/60157/ Copper is still better at conducting heat. But just a little bit of thermal-jumper to make that small electrical separation is all you need. Datasheet: https://www.vishay.com/docs/60157/thjp.pdf https://www.vishay.com/docs/60157/thjp.pdf In any case, modern material science provides us with plenty of useful insulators, conductors, thermal-conductors (but not electrical), semiconductors, and now semi-heat conductors (erm, thermal semiconductor?) I don't expect the thermal semiconductor to be replacing any of the other materials we already use. Instead, we will find new discoveries and applications for things I can barely imagine.
mitthrowaway2 3y ago
Perhaps another application is insulation of batteries. You want good thermal conductivity when the battery is in active use at high power draw to sink heat to the environment, but also you may want to insulate it when it's idle and freezing outside, to reduce how much self-discharge is needed to maintain its minimum temperature. However, it might be simpler to do this with moving parts or phase-change materials, etc
c22 3y ago
You could switch the thermal sink between multiple radiators to give each one a lower duty cycle.
- dragontamer 3y ago
  Heat naturally flows to the lowest temperature object connected by the lowest thermal-resistance (or highest thermal conductivity). If you have a radiator at 80C, and a 2nd radiator at 60C and both are connected to HotPlate-X, the heat will naturally find itself going to the 60C, while the 80C will more naturally find its own heat radiating out to the environment quicker. You don't need a thermal-semiconductor to just have heat flow around. That's just... heat physics. -------- There seems to be some practical applications for this new "thermal semiconductor". Though the next questions are that of cost, performance, etc. etc.
  - jfoutz 3y ago
    it (the insulator) seems very small. I think, a lot of chips have multiple temperature sensors across the whole chip to decide when to clock down. If I have 4 cores, and 1 is going flat out, I could see insulating the unused (or lesser used) cores. The idea being give the hot part the full cooling capacity. That seems like the obvious idea. But maybe I'm misunderstanding or forgetting something fundamental.
    - LoganDark 3y ago
      > The idea being give the hot part the full cooling capacity. Isn't it also to prevent the hot part from heating the other, cooler parts? This could be used to give each part of a CPU its own independent cooling. That'd be pretty cool.
    - yetihehe 3y ago
      You can use this to equalize temperatures on one chip, using it like a changeable heat-shield, so instead of hotspots, you artifically keep some heat from escaping from colder areas too fast which could prevent stress induced cracking. It's better to keep whole chip at 70*C than a one small area at 70 and other areas at 30. Then when heat load from that one small spot vanishes or is moved to other spot, you can change your heat mask on the fly.
amelius 3y ago
> Cooling of CPUs is awful use of this tech. Why would anyone turn down thermal conductivity? Well, you could build logic gates out of these switching elements ;)

Terr_ 3y ago

> I wonder what applications it will find? New analogies for Maxwell's Demon. :p This out of left-field, are there any military applications in when it comes to vehicles' appearance in thermal imagery? I suppose you wouldn't need something like this for the relatively slow switching of stuff like "which side of the tank should be the hot side".

yetihehe 3y ago
> are there any military applications in when it comes to vehicles' appearance in thermal imagery? Yeah, you can now display moving images for thermal imagers, like showing the temperature of terrain behind vehicle while moving around.
- Terr_ 3y ago
  It sounds like that depends on having outer tiles with basically no heat capacity so that each cools instantly... Or else something ready to pump the heat away.
  - yetihehe 3y ago
    Yeah, like a thermal transistor. When temperature transfer is blocked, outer surface of that transistor should pretty fast go to ambient air especially with moving air. Remember that transistor is only several atoms thick and can switch at megahertz speeds.

Sanzig 3y ago

Definitely would be really interesting for spacecraft thermal management. Spacecraft only have radiation as a heat transfer mechanism, and they need to be designed to keep all components within a safe temperature under a range of operating conditions (eg: from receiving no sun on the dark side of a planet to full sun a few minutes later). A satellite in low earth orbit can experience a dozen or more sun/eclipse cycles per day, which makes thermal cycling a major factor in long-term reliability. Moving parts are strongly discouraged for reliability reasons, so thermal design needs to be as passive as possible. Having a solid state switched thermal conductance path would be a huge benefit. Imagine being able to switch a radiator off in eclipse to conserve heat and on in sun to reject it.

__MatrixMan__ 3y ago

A device that makes jesus toast (other images too I guess).

jjk166 3y ago

I would think the ideal use case would be for scientific equipment where a very precise temperature needs to be maintained. Right now you either have a large thermal mass to prevent fluctuations (which also means you can't quickly and precisely vary the temperature), or you just accept the thermal noise and try to compensate for it in the analysis.