Scientists Develop 'Invisibility Cloak'—With a Catch

The cloak makes objects invisible to microwave light.


Invisibility cloaks could soon hide more than just Harry Potter, shown here in a scene from "Harry Potter and the Deathly Hallows: Part 2."

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Harry Potter fans and secret agents, take note: Scientists at the University of Texas, Austin have developed an "invisibility cloak." The catch is that, for now at least, it only shields objects from microwave light.

The researchers are optimistic that they will someday be able to develop similar technology to hide an object from visible light. The cloak was able to hide a 7-inch long rod using copper tape and an extremely thin (100 micrometers) polycarbonate film.

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The film scatters the microwaves given off by an object giving an "overall effect [of] transparency and invisibility at all angles of observation," says Andrea Alu, one of the authors of the study.

They say that the cloak needs no battery power, making it a "passive" device.

"It's a passive layer, you just put it on top and it works," he says. "Think of it as a piece of plastic wrap—it's a transparent layer you can wrap around an object. We can remove it and put it back on."

The process can be applied to extremely small objects to make them completely invisible, even to the human eye—but for now it only works with microscopic objects.

"In principle, this technique could also be used to cloak light," he says. "When applied to optical frequencies, we may be able to efficiently stop the scattering of micrometer-sized objects."

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Making an object invisible to microwave light could have important military implications, Alu says. Cloaking large objects such as a tank or plane would be difficult with current technology, but specific telecommunications devices could be covered, making them immune to tampering or interference.

"We could make antennas and sensors invisible, so we wouldn't have problems with interference," he says.

He says the process can be applied to cloak any shape, but that each film must be custom made for a specific object. The cloaking material is not expensive, but design costs could be.

"They could be produced quite cheaply, but they have to be designed and tailored for a specific object," he says. "The main challenge is to get the recipe for each object. The technology itself is not expensive."

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