Microfluidic Cooling Turns Down the Heat On High-Tech Equipment

An anonymous reader writes with a snippet from HelpNet Security about a technology that sounds promising down the road for consumer equipment, but may land a lot sooner than that in high-end applications where cooling is critical: Thousands of electrical components make up today's most sophisticated systems – and without innovative cooling techniques, those systems get hot. Lockheed Martin is working with DARPA on its ICECool-Applications research program that could ultimately lead to a lighter, faster and cheaper way to cool high-powered microchips – by cooling the chips with microscopic drops of water. This technology has applications in electronic warfare, radars, high-performance computers and data servers. The micro-cooler is only 250 microns thick, and 5 millimeters long by 2.5 millimeters wide.

Comments

Really?

[ledow]

It might allow you to spread the heat or avoid direct water transfer but you still have to move that heat somewhere. You're not REDUCING the heat, are you? It's still producing the same amount of heat and you're still needing to get rid of it.

At the end of the day, whatever fancy technique you use, there's still going to be a large bit of aluminium somewhere, and probably a cheap fan blowing over it. If not, then you're into things more complicated, fragile or liquid than you want them to be.

The only other cooling technology I've seen was a heat-pipe cooled PSU that I still have. No moving parts at all, just clever design, and natural air-flow. But things like that aren't scaling and can't be used on more heat-generating parts (do PSU's really generate that much heat?).

No matter how you look at it, whether you water-cool or whatever, you still need a big piece of metal with huge surface area being cooled somehow to actually "get rid" of the heat. Everything else is just a matter of the efficiency or difficulty of how you get the heat to that point.

With consumer items like laptops and desktop PC's, you're not going to change anything. And bigger things like cars, planes, etc. don't really have a problem - localised heating might be problematic but space isn't at such a premium that you can't solve it with "normal" techniques and a huge heatsink (i.e. the bodywork).

However, I still don't get why all laptops / tablets don't just have a large metal base inside their plastics to just spread the heat over everything, so you don't get one burned thigh and one cold thigh.

Re:Really?

[occasional_dabbler]

You have missed the point of the device, even though you identified the problem it is solving:

Everything else is just a matter of the efficiency or difficulty of how you get the heat to that point..

It reduces the thermal resistance between the chip and the heat sink, so for a given installation and heat rejection rate the chip itself will be cooler.

...bigger things like cars, planes, etc. don't really have a problem... ...a large bit of aluminium somewhere, and probably a cheap fan blowing over it.

You do not add any weight to an aircraft that isn't absolutely necessary and you do not add any kind of active device where a passive one could work because of reliability. Keeping electronics cool in an aircraft is a very complex and expensive problem. Keeping a chip even two or three degrees cooler will have a measurable effect on the reliability over the aircraft life.

Re:Really?

[fuzzyfuzzyfungus]

To the best of my understanding the improvement here is in lowering the thermal resistance right at the point of contact between the IC and the cooling system, which doesn't change the fact that the waste heat still has to go somewhere; but does allow heat to be removed from that very small contact area faster, which increases the safe maximum wattage for a given die size.

It requires good engineering to do robustly, quietly, in a relatively compact unit, etc; but dumping large amounts of waste heat once you've gotten it into the cooling system is the relatively easy part. We'll always wish we could get away with something lighter or smaller or quieter; but we can build you a heat exchanger large enough to throw at pretty much any thermal load(chips are very much on the low end: engine cooling can easily bring you into the multiple kilowatts and power plant heat exchangers into the multiple megawatts); but what we cannot so easily do is move heat faster from a small, fixed, dissipation area. If your IC is only 1 square cm, you have to be able to extract all the waste heat generated by the power level you are operating it at through that single square cm, with a low enough delta T to keep the IC from cooking itself.

The relatively simple method is just a solid heat spreader; but if you want to hit power densities higher than the conductivity of copper will allow, you have limited options(diamond would be nice, if you can get in the size you need). Direct liquid cooling of the die is tricky, even if you have access to cryogens, because the Leidenfrost effect tends to produce an insulating layer of vapor right where you don't want it, surrounding the item to be cooled, which ruins the efficiency of heat transfer. My understanding is that this microfluidic apparatus is aimed at solving this problem; by forcing the liquid coolant onto the chip in a way that disrupts the vapor layer in a way that naive 'just pour it on/pump it across' approaches don't.

It might prove to be the case, especially if somebody comes up with a clever way of producing the stuff in bulk, that these microfluidic interfaces will end up being used in larger cooling applications as well; but at present they are aimed at the problem of cooling small, relatively fixed size(since die area is expensive; and sometimes design constraints related to clocking and signal propagation time don't even allow you to spread the same circuit over a larger die, even if you are willing to pay for the extra area), heat sources that are bumping up against the limits of how fast we can get heat away from them. Whatever cooler ends up dumping the heat into the atmosphere or chilled water supply or whatever will be purely conventional; it's the point of contact between the IC and the conventional cooling system that is being improved.

Re:Really?

[DigiShaman]

...a power supply rated at 500 W can deliver 500 W of power to the system regardless of its efficiency, the efficiency tells you how much power it must draw from the wall to deliver those 500 W it does not affect its output capacity, a 500 W power supply that is 90% efficient can deliever the same amount of power as one that is only 80% efficient. If the power supply is 80% efficient it needs 625 W(500/0.8) from the wall, those extra 125 W are turned into heat by the power supply, while a 90% efficient unit would only be drawing 555 W from the wall, meaning it is dissipating only 55 W as heat, or only 44% of the heat the 80% efficient unit was creating.

- Toms Hardware

You fools!

[fuzzyfuzzyfungus]

Surely DARPA has enough nerds on hand to know that adding a 'small thermal exhaust port' to expensive military hardware is going to end in disaster, no?