New Version of Invisibility Moves Closer to Visual Cloaking

By Nina Bai | January 16, 2009 12:21 pm

invisibilityResearchers 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].

Related Content:
80beats: Light-Bending Scientists Take a Step Closer to Invisibility

DISCOVER: How to Build an Invisibility Cloak

Image: Duke University Photography

CATEGORIZED UNDER: Physics & Math, Technology
  • Stuart

    “wavelengths of microwave radiation ranging from about 1 to 18 gigahertz” – get it right! I thought this was a science blog?

  • Nina Bai

    Thanks. Corrected to “frequencies.”

  • nick

    Right, but we should be talking about wavelength of these photons, not the frequency (though they are inversely related), when we’re talking about bending light, as the wavelength dictates how it interacts with a material. So you might want to say that this material can work with wavelengths of light in the 5 to 50 centimeter range. (A rough non-calculated approximation of 18 to 1 gigahertz part of the electromagnetic spectrum). This range includes the microwaves we use to cook our food, though that deals with the frequency side of the equation.

    In any case, welcome to the blog, Nina.

  • Greg

    Amazing how life imitates art. Devices with such capability were considered science fiction until recently. It looks like the applications for this research is flying along much faster than expected. The debate should begin now on how to regulate it. The military applications are obvious, but privacy concerns are enormous.

  • Mike

    That would be great for space suits that block uv, x-rays and gamma rays, and space craft as well.

  • Chubbee

    Masked a 1 inch bump? WOW! Double that and I can walk around naked!


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