January 16, 2009

Cloak of Invisibility Close to Reality

A real cloak of invisibility is no longer hidden to researchers at Duke University, who developed a material that can "cloak" an item from detection by microwaves.

In fact, scientists said that they have even expanded the number of wavelengths they can block.

In 2006, the team reported they had developed " meta materials" that could deflect microwaves around a three-dimensional object, making it invisible to the waves.

The system works like a mirage, where heat causes the bending of light rays and cloaks the road ahead behind an image of the sky.

Beyond possible military applications, it also might have a very practical use by making mobile communications clearer.

"Cloaking technology could be used to make obstacles that impede communications signals 'disappear,'" said David Smith of Duke University in North Carolina, who worked on the study published in the journal Science.

Smith was part of the same research team that in 2006 proved such a device was possible.

He said the new material is easier to make and has a far greater bandwidth. The new cloak is made up of more than 10,000 individual pieces of fiberglass arranged in parallel rows.

Smith said they developed a series of mathematical commands to guide the development of more types of meta materials to cloak objects from an increasing range of electromagnetic waves.

"The new device can cloak a much wider spectrum of waves - nearly limitless - and will scale far more easily to infrared and visible light. The approach we used should help us expand and improve our abilities to cloak different types of waves," said Smith.

He said the goal was not to make something visible disappear. Cloaking can occur anywhere on the electromagnetic spectrum.

"Humans 'see' using visible light, which has wavelengths just under a micron (a millionth of a meter). But cell phones and other wireless devices 'see' using light that has a wavelength on the order of many centimeters," Smith said.

He said objects could block the "view" of these devices, making mobile phone communications more difficult.

"You might have two or more antennas trying to 'see' or receive signals, one being blocked by the other," he said. "You could imagine adding cloaks that would make one antenna invisible to the next, so that they no longer interfered."

Smith said the notion of a device that makes objects invisible to people is still a distant concept, but not impossible.

"This latest structure does show clearly there is a potential for cloaking -- in the science fiction sense -- to become science fact at some point," he said.

While the study's funders included Raytheon Missile Systems and the Air Force Office of Scientific Research, Smith said the technology is not intended to replace "stealth" technology.

"Just about all technologies that have any application, naturally have potential in military applications," he said.

"If this has an impact on communications applications, even commercial, those same applications presumably exist in defense contexts."


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