First demonstration of a working invisibility cloak
from Inventors and Remarkable People (112 articles)
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Image Gallery ( 3 images )October 20, 2006 A team led by scientists at Duke University's Pratt School of Engineering has demonstrated the first working "invisibility cloak." Now before you get all excited about the prospects of playing the invisible man or Harry Potter, it’s not a Dr Zhivago sort of cloak but an electromagnetic radiation cloaking device and we’re many years from being able to turn an object or person invisible to the naked eye. The cloak deflects microwave beams so they flow around a "hidden" object inside with little distortion, making it appear almost as if nothing were there at all. Cloaks that render objects essentially invisible to microwaves could have a variety of wireless communications or radar applications, according to the researchers. Watch the video.
The team reported its findings on Thursday, Oct. 19, in Science Express, the advance online publication of the journal Science. The research was funded by the Intelligence Community Postdoctoral Fellowship Program. The researchers manufactured the cloak using "metamaterials" precisely arranged in a series of concentric circles that confer specific electromagnetic properties. Metamaterials are artificial composites that can be made to interact with electromagnetic waves in ways that natural materials cannot reproduce. The cloak represents "one of the most elaborate metamaterial structures yet designed and produced," the scientists said. It also represents the most comprehensive approach to invisibility yet realized, with the potential to hide objects of any size or material property, they added.
Earlier scientific approaches to achieving "invisibility" often relied on limiting the reflection of electromagnetic waves. In other schemes, scientists attempted to create cloaks with electromagnetic properties that, in effect, cancel those of the object meant to be hidden. In the latter case, a given cloak would be suitable for hiding only objects with very specific properties.
"By incorporating complex material properties, our cloak allows a concealed volume, plus the cloak, to appear to have properties similar to free space when viewed externally," said David R. Smith, Augustine Scholar and professor of electrical and computer engineering at Duke. "The cloak reduces both an object's reflection and its shadow, either of which would enable its detection."
The team produced the cloak according to electromagnetic specifications determined by a new design theory proposed by Sir John Pendry of Imperial College London, in collaboration with the Duke scientists. The scientists reported that theoretical work in Science earlier this year.
The principles behind the cloaking design, though mathematically rigorous, can be applied in a relatively straightforward way using metamaterials, said cloak designer David Schurig, a research associate in Duke's electrical and computer engineering department
"One first imagines a distortion in space similar to what would occur when pushing a pointed object through a piece of cloth, distorting, but not breaking, any threads," Schurig said. "In such a space, light or other electromagnetic waves would be confined to the warped 'threads' and therefore could not interact with, or 'see,' objects placed inside the resulting hole."
The researchers used a mathematical description of that concept to develop a blueprint for a cloak that mimics the properties of the imagined, warped space, he said.
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