Duke scientists set sights on cloak of invisibility
Artificial materials may make science fiction dream a reality
BY JON VAN

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.
Really.

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."