Invisibility a Reality?

August 1, 2006
Cloaking device: schematics for Star Trek's Romulan Warbird
Cloaking device: schematics for Star Trek's Romulan Warbird

If the efforts of Duke researchers and their English colleagues come to fruition, Harry Potter may no longer possess the world's only known invisibility cloak. The researchers from the Pratt School of Engineering and Imperial College of Science, Technology and Medicine, in London, say they have developed the blueprint for an invisibility cloak that could hide any object so well that observers would be completely unaware of its presence. The cloak potentially has numerous applications, from defense to wireless communications.

In principle, an invisibility cloak could be realized with exotic artificial materials called "metamaterials." First demonstrated by David R. Smith, a professor of electrical and computer engineering at the Pratt School, and his colleagues in 2000, metamaterials can be made to interact with light or other electromagnetic waves in precise ways.

Although the theoretical cloak now reported has yet to be created, the Duke researchers are on their way to producing metamaterials with suitable properties, Smith says. "The cloak would act like you've opened up a hole in space. All light or other electromagnetic waves are swept around the area, guided by the 'metamaterial' to emerge on the other side as if they had passed through an empty volume of space." Electromagnetic waves would flow around an object hidden inside the cloak just as water in a river flows virtually undisturbed around a smooth rock, Smith adds.

The research team, which also includes David Schurig, a Pratt research associate in electrical and computer engineering, and John Pendry of Imperial College, reported its findings in Science Express, the online advance publication of the journal Science.

"There are several possible goals one may have for cloaking an object," says Schurig. "One goal would be to conceal an object from discovery by agents using probing or environmental radiation."

"Another would be to allow electromagnetic fields to essentially pass through a potentially obstructing object," he says. "For example, you may wish to put a cloak over the refinery that is blocking your view of the bay."

By eliminating the effects of obstructions, the cloaking also could improve wireless communications, Schurig says. Along the same principles, an acoustic cloak could serve as a protective shield, preventing the penetration of vibrations, sound or seismic waves. The scientists say their next major goal is an experimental verification of invisibility to electromagnetic waves at microwave frequencies.