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Duke University Scientists Create Invisibility Cloak


More than a century ago, English novelist H.G. Wells wrote about The Invisible Man. Ever since then, invisibility has been a staple of science fiction. This week, invisibility moved from science fiction to science fact. But it's still a long way from the kind of invisibility you're probably imagining.

A research team at Duke University in North Carolina has demonstrated the ability to make things disappear, at least in a very limited way. What they did is devise a way of steering one particular frequency of microwaves around an object so that, if your eyes were sensitive only to that microwave frequency instead of visible light, the object would seem to disappear.

In the 1990s, a physicist named Lawrence Krauss came out with a book called The Physics of Star Trek. In it he described how an alien species called the Romulans made their spacecraft invisible by warping space so light rays bend around it. So I asked the David Schurig, co-author of this week's invisibility paper, if that's what they did.

"Yes, functionally that's exactly what we're doing," he said. "The only difference is the Romulans are using some sort of space warp to do it, and we're using a material shell and the properties of that material being designed in a very specific way to bend the light rays around the object."

We see stuff because light reflects off it. If the rays are curved or bent, they don't bounce back from the object, and there's nothing to see. To guide the microwave rays around their target, Schurig and his colleagues turned to a metamaterial.

"Metamaterials are artificially structured composites that are a new way of tailoring the response - in our case, the electromagnetic response - of materials into areas that were not previously available," Schurig said.

The material of copper and fiberglass resembles printed circuit board with a geometric pattern tuned to a particular frequency. "So instead of relying on chemistry," Schurig continued, "we use artificial structuring and patterning to get the response we want, and it gives us a wider range of capabilities for the material."

Another member of the team said they are still a long way from the kind of invisibility imagined by science fiction writers.

"When you think of cloaking or invisibility, you think of making something vanish," said David Smith. "And usually you think of it optically vanishing, or you look at something and then it's gone. And right now we don't know how to do that. This is just a simple example where you can take one wavelength - for example, one color - and you could achieve cloaking of that color."

It may be a long time, if ever, before the science fiction kind of invisibility is achieved. In the meantime, the work that Smith, Schurig and their colleagues are doing at Duke University could find applications in communications, power-beaming - which is a technology for transmitting power through the air using microwaves or lasers - and, we have to also suspect, the military. The research was published Thursday online at SciencExpress.org.

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