An Invisibility Cloak For Heat

Scientists have found you can make objects invisible to heat -- without exotic materials.

Infrared sensors are able to peer into the night and see people in complete darkness because people give off body heat. But what if a person could wear clothing that makes their body heat silhouette invisible to infrared lenses?

Scientists in France are working on an invisibility cloak for heat and have reported their research in a recent issue of Optics Express. The technology could be used for military purposes to hide soliders from infrared detectors, but it could also work to thermally isolate circuits in computer chips, which would keep them cool.

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The team, lead by Sebastien Guenneau of the University of Aix-Marseille and colleagues at the French national research council, devised a mathematical model showing that a set of concentric rings, each one made of a material with differing diffusivity could cloak heat energy. Metal, for example, diffuses heat very well, while plastic doesn't. By alternating such materials, the heat flowed around the central region, essentially making it invisible. An infrared camera wouldn't pick it up because there would be no temperature difference between that region and its surroundings.

"The underlying idea is to guide heat around the region which you'd like to protect from thermal flux," Guenneau told Discovery News.

A key finding in this research is that the team realized cloaking heat would not require exotic, manmade materials, known as metamaterials, typically used to cloak objects from other kinds of light waves or even sound waves. That's good news for this kind of cloaking because it can use standard materials already available.

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Guenneau said the team didn't try to cloaking any human-sized objects from infrared light, though it's clear that the ability to shield them from infrared cameras would be of real interest to the military. Instead, their mathematical models focused micrometer-sized objects - the size range of most electronic components inside computer chips. Keeping these components cool is of big interest to the electronic industry, which spends millions of dollars just trying to keep Internet servers from overheating, not to mention individual laptops.

The next step is to actually fabricate a device –- thus far the work has been in the area of mathematical modeling. It will take some work to find the materials that work best.

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