Scientists Develop Thermal Camouflage That Can Dupe Infrared Cameras (cosmosmagazine.com)

Writing in the journal Nano Letters, scientists from Turkey, the U.S. and U.K. describe a material that acts as thermal camouflage. Cosmos reports: Coskun Kocabas and colleagues created a film comprising multiple ultra-thin layers of graphene and a bottom layer of gold, with non-volatile ionic liquid in between them. When a small current is applied, the ions move up into the graphene layer, cutting down the infrared radiation the surface would normally emit. Because it's thin, light and flexible the film can be applied to any number of surfaces, including clothing. Tests have successfully camouflaged a hand owned by a subject wearing a covering of the material, and others have shown it to be indistinguishable from its surroundings in a variety of ambient temperatures.

Comments

Thick clothes

[DrYak]

You radiate IR for some very good reason.

Yup, you're losing thermal energy.

For years, "thermal camo" has basically boiled down to "a layer of very well insulating clothes" (and face paint, and gloves).

The thing is, in a very hot climate, wearing insulating clothes will make you feel hot.
You would need to undress a bit, which might not be practical in every situation.

If you are wearing a suit of this stuff I imagine you won't be wearing it a long time.

The whole point of this tech is that it's switchable between isolating and radiating mode.
At a single button you can basically transform it from a wool sweater to sport T-shirt and back, without need to remove any layer of clothes (unlike classical thermo camo).
You only turn it on where thermal camouflaging is necessary, instead of wearing an isolating layer for the whole time.

Re:Where does it go?

[careysub]

The summary and the article abstract do no make this clear but what that this device does is change the emissivity of the surface in the thermal IR band, which is around 10 microns. This means it simply alters the thermal emission - it makes is "white" or "black" (or shades of grey) in the IR band, which is far below normal optical bands, to match whatever the emission of the background is.

The optical band appearance of an object tells you nothing about its thermal IR band appearance. Two common materials that are pitch black in the thermal IR band: pure water and regular glass. Clean polished metal surfaces are reflective in both, but if it was could covered with an IR band black paint, and you would be none the wiser visually.

What effect would it have on body temperature regulation? Thermal radiation is only one of three ways your body disposes of metabolic heat under normal circumstances - the other two are convection and evaporation (which also works with convection but is a separate mechanism). The first two (radiation, convection) work both ways - you can gain heat, not lose it in a hot environment. There is also conduction but you have to be in physical contact with a surface for this to happen, so it is not the usual case for a camouflaged soldier unless wading (it is also in principle a two way process).

So modulating thermal emission changes only one of three (or four) ways of controlling core temperatures, requiring the others to take up the slack.The contribution of thermal emission to body temperature regulation varies with the environmental temperature. At about 33 C it is zero, since this is skin temperature. At higher environment temperatures you can only gain heat this way, not lose it - so being IR white is better. At low temperatures you can lose a lot, and if this bad being IR white is again helpful. But if you need to lose heat to keep from overheating, and the environment is below body temperature then being IR black is good. In general thermal radiation is the least important of the three (or four) processes, becoming dominant only when its cold and you will be snug in your parka anyway.

Is this is a new development, or a same old-same old story with a tweak?

This is looks like a genuine breakthrough of an amazingly cyberpunky kind, the sort of thing science fiction has been famous for "predicting" before it became available. The essential point is that thermal IR emissions are from the true surface of the material. You can't have a "layer of something" on top of the material with the variable emissivity, because then that would be the surface doing the emitting. You must genuinely change the surface properties with something behind the surface. This is a genuine IR optical "paint" that changes color electronically!

And the fact that it uses graphene, nanotubes, and ionic liquids combines buzz-word tech to the nth degree!

You can get the article using Sci-hub.