Duke scientists set sights on cloak of invisibility
After years of work, David Schurig and David R. Smith at Duke University will finish their research and have absolutely nothing to show for it: They're making a cloak of invisibility.
So unusual is this undertaking for a serious academic electrical engineering team that Smith has created an elaborate Web site discussing the dream of invisibility as viewed in science fiction--Harry Potter and the Hogwarts School of Witchcraft are mentioned--and relating such ideas to scientific fact.
In theory, Smith said, it's possible to make light follow curved lines that skirt an object rather than illuminate it. Light "circulates around the void--like water flowing past a rock in a stream," Smith explained.
This would create a void in space--a place that is invisible.
It's an interesting theory cooked up by Smith and Sir John Pendry at the Imperial College in London. Even more interesting will be to see if the theory will produce invisibility.
Equations describing the properties of electromagnetic fields were derived in the 19th Century by James Clerk Maxwell, and they can be used to envision how substances would deflect light, said Schurig.
Natural materials would not do the trick, but Duke researchers are designing artificial substances, called metamaterials, that are engineered to be invisible. They use technology for making circuit boards and computer chips to create metamaterials.
"We're building stuff in the microwave range, using fairly standard lithography," said Schurig.
The metamaterials under construction should render an object invisible to radar, although people could still see it, said Schurig. The Duke team's goal is to have a working example sometime next year. It would demonstrate that invisibility cloaks can work.
The project has evoked interest from military people who like the idea of cloaking spy satellites so they are invisible to radar, among other things. The Defense Advanced Research Projects Agency is financing the research.
Making a cloak to render stuff invisible to the human eye will be more difficult, requiring nanotechnology fabrication and some very clever design work, Schurig said.
"It will probably take 10 years, and we're not certain it's possible," he said.
Visible light waves are shorter than the microwave spectrum in which the researchers are working, and human vision sees light at several wavelengths. It's not clear if metamaterials can be designed to deflect light at several wavelengths simultaneously.
But even if an invisibility cloak isn't perfect it could be useful, said Schurig.
"You might make a cloak against infrared light," he said, "so that someone using night vision goggles couldn't see you."
Deflecting green light might make someone moving in a jungle virtually invisible.
Smith cites the film Predator, in which an alien has a cloak that provides imperfect invisibility that still works pretty well.
"Along the lines of advanced camouflage, we should not overlook the solutions that nature has provided," Smith said on his Web site. "An object is invisible if it is indistinguishable--or at least hard to distinguish--from its surrounding environment. Many animals and insects have evolved in form to blend into their environment, making it harder for predators . . . to find them."
Metamaterials might be used to cloak structures that block radio signals, thereby improving cell phone communications, Schurig said.
"Many people have this fantasy of being invisible," he said. "It's not clear what the commercial benefits might be, but the idea has really sparked a lot of interest."
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