U.S., UK scientists invent invisibility cloak
In "The Lord of the Rings" elves gave Frodo The Ringbearer a cloak of invisibility to shield him from Orcs, Harry Potter had a similar garment, and the Romulans used a "cloaking" device to sneak up on Capt. James Kirk and the spaceship Enterprise in "Star Trek" episodes and movies.
The "Invisible Man" is a classic 1933 scifi flick adapted from an H.G. Wells ("War of the Worlds," "The Time Machine") novel in which a scientist discovers a way to become invisible, then becomes murderously insane. The movie was resurrected in 1992 by director John Carpenter, then sequeled by "Hollow Man."
Elves, hobbits, witches, aliens, mad scientists -- all fiction or fantasy, but now researchers from the United States and Britain are making invisibility a reality and successfully cloaked a copper cylinder.
"We have built an artificial mirage that can hide something from would-be observers in any direction," said cloak designer David Schurig, a research associate in Duke University's electrical and computer engineering department.
The cloaking of a cylinder from microwaves comes just five months after Schurig and colleagues published their theory that it should be possible. Their work is reported in a paper in Friday's issue of the journal Science.
"We did this work very quickly ... and that led to a cloak that is not optimal," said co-author David R. Smith, also of Duke. "We know how to make a much better one."
For their first attempt, the researchers designed a cloak that prevents microwaves from detecting objects. Like light and radar waves, microwaves usually bounce off objects, making them visible to instruments and creating a shadow that can be detected.
The first working cloak was in only two dimensions and did cast a small shadow, Smith said. The next step is to go for three dimensions and to eliminate any shadow.
Viewers can see things because objects scatter the light that strikes them, reflecting some of it back to the eye.
"The cloak reduces both an object's reflection and its shadow, either of which would enable its detection," Smith said.
The cloak is made of metamaterials, which are mixtures of metal and circuit board materials such as ceramic, Teflon or fiber composite.
In an ideal situation, the cloak and the item it is hiding would be invisible. An observer would see whatever is beyond them, with no evidence the cloaked item exists.
Natalia M. Litchinitser, a researcher at the University of Michigan department of electrical engineering and computer science who was not part of the research team, said the ideas raised by the work "represent a first step toward the development of functional materials for a wide spectrum of civil and military applications."
Joining Schurig and Smith in the project were researchers at Imperial College in London and SensorMetrix, a materials and technology company in San Diego, Calif.
The research was supported by the Intelligence Community Postdoctoral Research Fellowship Program and the United Kingdom Engineering and Physical Sciences Research Council.
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