Researchers who created the first so-called invisibility cloak in 2006, have made significant advances that could lead to an invisibility cloak for visible light in as little as six months. “A large number of folks are looking at it, and I think it’s a matter of coupling the right material to the right device,” [Discovery News] said researcher David Smith. His team has developed an algorithm that speeds up the design of materials that can bend light around an object. Using the new algorithm, they were able to create an invisibility cloak that can bend much wider spectrum of microwaves than previous versions.
Invisibility cloaks rely on metamaterials, ones with unique properties that derive from [their] physical structure, not [their] chemical make up [Discovery News]. Smith compares the effect of metamaterials on light to mirages that appear over a road on sweltering days. “You see what looks like water hovering over the road, but it is in reality a reflection from the sky,” Smith said. “In that example, the mirage you see is cloaking the road below. In effect, we are creating an engineered mirage with this latest cloak design” [AFP].
The new cloaking device measures 20 inches by 4 inches and is made up of 6,000 I-shaped copper structures placed on a circuit board. Whereas previously, researchers needed to individually calculate the dimensions and placement of each copper piece, an extremely time-consuming process, the new algorithms automate the task; the team designed and made the new cloak in just ten days. The researchers report in Science [subscription required] that the new cloak works with frequencies of microwave radiation ranging from about 1 to 18 gigahertz. (To manipulate light, the microscopic surface of a material must be much smaller than that of the wave length of light being used [Discovery News], so the smaller the wavelength of light, the harder it is to cloak.) They were able to hide a one-inch bump using the new cloak. But the new cloak does have limitations: It only works in two dimensions. Both the background and the hidden object must also both be wrapped in the metamaterial [Discovery News].
If these limitations can be overcome, invisibility cloaks could have endless applications. They could remove cell-phone interference, allowing clear reception even in elevators, suggested Smith. “By eliminating the effects of obstructions, cloaking devices could improve wireless communications, or acoustic cloaks could serve as protective shields, preventing the penetration of vibrations, sound or seismic waves,” said the team [AFP]. Unlike so many other cutting-edge technologies, the invisibility cloak is also cheap to produce. Smith’s rough estimate was that it took about $1.00 in circuit boards to cloak the one-inch bump on the metamaterial. “If you were to commercialize this technology it would cost next to nothing,” said Smith [Discovery News].
80beats: Light-Bending Scientists Take a Step Closer to Invisibility
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Image: Duke University Photography