Two New Cloaking Devices Close In on True Invisibility

Richard A. Lovett
for National Geographic News
May 6, 2009

Cloaking devices, like the Star Trek technology that can make whole Romulan warships disappear, came a step closer to reality last week.

Two independent teams have developed silicon-based materials that can hide microscopic objects. The materials are the first to work in near-infrared light, wavelengths very close to visible light.

On a flat surface, an object covered with a piece of cloth would normally be detectable based on its telltale bump. But with the new materials, even the bump seems to vanish.

A team led by Xiang Zhang at the University of California, Berkeley, achieved this effect by drilling scores of tiny nano-holes into the cloaking material.

(See pictures of materials that use nanotechnology.)

These holes change the material's optical properties, allowing light to bend around the hidden object, as described in the April 29 issue of Nature Materials.

The other team, led by Michal Lipson at Cornell University, achieved the same effect by covering their material's surface with tiny pillars also designed to bend light. The Cornell group's paper is currently under review by Nature Photonics.

Jason Valentine, one of the Berkeley researchers, calls his team's material a "carpet cloak." In both cases the process is like hiding something beneath a rug.

"The object is effectively hidden on the ground," Valentine said.

Small But Effective

Both materials still have a long way to go before they're ready for stealth military operations. To start with, both cloaks work only in infrared light for now. The next step is to try to develop a version that works in visible wavelengths.

The cloaks are also capable of hiding only microscopic objects.

Continued on Next Page >>


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