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Scientists come a step closer to invisibility cloak

Posted at 7:39 AM, Mar 27, 2013

By Ben Brumfield

(CNN) — Some scientists seem to take their cues from science fiction or fantasy novels.

Physicists in Texas have developed a method to make objects “invisible” within a limited range of light waves. It’s not Harry Potter’s invisibility cloak just yet, but scientists say it has a lot of potential.

The desire to become invisible dates to the ancient Greeks, if not further. In mythological literature, gods and goddesses donned a headdress to disappear from sight. Like Potter’s cloak, the “cap of invisibility” was imbued with magical powers.

A fixture in magic, the invisibility cloak has now advanced to science.

Researchers at the University of Texas in Austin have developed a thin material called a ‘mantle cloak,’ according to a report published in the New Journal of Physics Tuesday.

If an object is wrapped in it, it ‘disappears,’ but the effect only applies to a limited range of light waves — specifically microwaves.

The future is not here just yet

In their experiment, the physicists covered a cylinder about a foot long and an inch or so in diameter with the material. Microwave detectors could no longer plainly ‘see’ it, although it was still visible to the human eye. But the same principle could be transferred to the range of perceptible light, researchers say.

Doing so would then make objects invisible to the human eye.

The effect only covers a very small band of electromagnetic waves at one time, and in the visible range of light, it would only work on objects much thinner than a single strand of hair.

Useful in nanotechnology

Scientists, on the other hand, find this development exciting because it could prove useful in nanotechnology by letting light bypass microscopic objects that would otherwise block it.

The discovery could advance the fields of specialty optics and biotechnology, according to the physicists.

This is not the first time scientists have made an object ‘invisible,’ but previous methods have involved hulking devices and more cumbersome methods.

The new cloak is made of a sheer, handy material that can be applied to many surfaces, even irregular ones, according to the report.

Light and invisibility

We see things because light reflects off of them and hits our eyes. Or, in this case, microwaves bounce off of them and hit a detection device.

Light has properties that can be manipulated, which is how objects can be rendered invisible. It can be reflected away, for example. Illusionists such as David Copperfield can use mirrors to make an object disappear.

Light also refracts — or breaks — when it passes through a prism or raindrops, resulting in the palette of colors we see in a rainbow. It also bends ever so slightly due to gravity, when it passes by a planet.

Previous attempts at achieving invisibility have involved bending or reflecting light around the object that is meant to vanish.

The mantle cloak takes a new approach.

Light is a wave that can be disturbed. That’s what the mantle cloak does.

The cloak’s material

It is made by combining copper tape with polycarbonate, a material commonly used in DVD’s and CDs. The resulting cloak has a miniscule pattern — like a finely checkered shirt — that neutralizes the waves bouncing off of it.

For it to work, the material’s pattern has to be roughly the size of the wavelength of light to be canceled out. That gives it a tightly limited range of waves it will work on.

It has no effect on a vast array of electromagnetic waves, which come in a myriad of sizes. The light waves we can see make up only a thin sliver of them.

Although the scientists say the principle behind the cloak could currently only be used to hide objects from the human eye that are so tiny it can’t see them anyhow, they say it could “pave the way” to the development of advanced “camouflaging and invisibility.”

Microwaves, which the mantle cloak currently does neutralize, are used in radar detectors.

Perhaps the cloak would make a good ingredient in car paint.