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Wednesday, March 27, 2013


The scientific pursuit of invisibility --- a la the cloak of invisibility used by the world's most popular fictional wizard, Harry Potter --- has in the past been weighed down by a number of rather cumbersome inventions.

But, now, a research team from the University of Texas at Austin has crafted a cloak that is just micrometers thick and can hide three-dimensional objects from microwaves.

Unveiling their study Tuesday in the Institute of Physics and German Physical Society's New Journal of Physics, the researchers explained how the ultrathin layer, called a "metascreen," is able to mask a 3D objects in a natural environment, from any direction microwaves might be coming, as well as anywhere an observer is positioned, according to a report in Science Daily.

The metascreen was made by attaching 66 micrometers-thick copper tape to a 100 micrometers-thick polycarbonate film, in a fishnet design.

The high-tech screen was used to cloak an 18 cm cylindrical rod from microwaves.

The researchers also said oddly shaped and asymmetrical objects can also be cloaked with the same principles.

Objects are detected when waves -- sound, light, x-rays or microwaves -- rebound off their surfaces. So, the reason we see objects is because light rays bounce off their surfaces toward our eyes, which are then able to process the information.

Whiles previous cloaking attempts used various metamaterials to divert, or bend, incoming waves around an object, the new method, named "mantle cloaking," uses an ultrathin metascreen specifically made from metal to cancel out waves as they are scattered off the cloaked object.

"When the scattered fields from the cloak and the object interfere, they cancel each other out and the overall effect is transparency and invisibility at all angles of observation," said co-author of the study Professor Andrea Alu.

Last year, the same group of researchers successfully cloaked a 3D object using a method called "plasmonic cloaking," which used more bulky materials to cancel out the wave scattering. Thev results from that work was as well published in New Journal of Physics.

Of course, one of the biggest goals of the scientific team is to hide an object from visible light.
"In principle this technique could also be used to cloak light," said Alu. "In fact, metascreens are easier to realize at visible frequencies than bulk metamaterials and this concept could put us closer to a practical realization."

By Erik Derr

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