Scientist tried to make the Invisibility cloak

American physical scientists to design a 'magic' cloak that utilizes broadband frequency to conceal objects or humans. This system review published in the Physical Review Letters journal.

Many "invisibility" techniques actually make objects more obvious, not less, the researchers found. (Picture from: http://www.bbc.co.uk/)

U.S. physicists find this invisibility cloak could only hide objects within a certain range of wavelengths of light or microwaves. In other frequencies, the new invisibility robes will make an object appear more obvious.

"Our active Cloak is a new concept and design, which aims to break through the limitations of existing magic cloak now and we demonstrate that it is possible to do," said Prof. Andrea Alu, from University of Texas in Austin.

A new ‘broadband’ invisibility cloak which hides objects over a wide range of frequencies has been devised. (Picture from: http://uniquedaily.com/)

"If you want to make an object transparent in all corners of the broadband frequency, this is a good solution. Technologies we tried to make it but at this time we are still in the early stages," he added.

The sphere on the right is "cloaked" but actually scatters more radiation than when bare (left). (Picture from: http://www.bbc.co.uk/)

The cloak is made from a thin shell meta material, which is an artificial composite structure allows the formation of properties that do not exist in nature.  Invisibility material is very useful for military purposes, microscopy, biomedical and energy producers.

Another ways to disappear:

1. Optical camouflage technology: A modified background image is projected onto a cloak of retro-reflective material (the kind used to make projector screens); the wearer becomes invisible to anyone standing at the projection source.
2. The "mirage effect": Electric current is passed through submerged carbon nanotubes to create very high local temperatures, this causes light to bounce off them, hiding objects behind.
3. Adaptive heat cloaking: A camera records background temperatures, these are displayed by sheets of hexagonal pixels which change temperature very quickly, camouflaging even moving vehicles from heat-sensitive cameras.
4. Calcite crystal prism: Calcite crystals send the two polarisations of light in different directions. By gluing prism-shaped crystals together in a specific geometry, polarised light can be directed around small objects, effectively cloaking them.

Prof David Smith of Duke University, one of the team who created the first cloak in 2006, said the new design was one of the most detailed he had yet seen. "It's an interesting implementation but as presented is probably a bit limited to certain types of objects," he told BBC News.

"There are limitations even on active materials. It will be interesting to see if it can be experimentally realised." Prof Smith points out that even an "imperfect" invisibility cloak might be perfectly sufficient to build useful devices with real-world applications.

For example, a radio-frequency cloak could improve wireless communications - by helping them bypass obstacles and reducing interference from neighbouring antennas. "To most people, making an object 'invisible' means making it transparent to visible wavelengths. And the visible spectrum is a tiny, tiny sliver of the overall electromagnetic spectrum," he told BBC News.

"So, this finding does not necessarily preclude the Harry Potter cloak, nor does it preclude any other narrow bandwidth application of cloaking." *** [EKA | FROM VARIOUS SOURCES | BBC | UNIQUE DAILY]
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