Invisibility cloak one step closer, scientists say
By Maggie Fox, Health and Science Editor
1 hour, 23 minutes ago

WASHINGTON (Reuters) - Scientists have created two new types of materials that can bend light the wrong way, creating the first step toward an invisibility cloaking device.

One approach uses a type of fishnet of metal layers to reverse the direction of light, while another uses tiny silver wires, both at the nanoscale level.

Both are so-called metamaterials -- artificially engineered structures that have properties not seen in nature, such as negative refractive index.

The two teams were working separately under the direction of Xiang Zhang of the Nanoscale Science and Engineering Center at the University of California, Berkeley with U.S. government funding. One team reported its findings in the journal Science and the other in the journal Nature.

Each new material works to reverse light in limited wavelengths, so no one will be using them to hide buildings from satellites, said Jason Valentine, who worked on one of the projects.

"We are not actually cloaking anything," Valentine said in a telephone interview. "I don't think we have to worry about invisible people walking around any time soon. To be honest, we are just at the beginning of doing anything like that."

Valentine's team made a material that affects light near the visible spectrum, in a region used in fiber optics.

"In naturally occurring material, the index of refraction, a measure of how light bends in a medium, is positive," he said.

"When you see a fish in the water, the fish will appear to be in front of the position it really is. Or if you put a stick in the water, the stick seems to bend away from you."

These are illusions caused by the light bending when it moves between water and air.

NEGATIVE REFRACTION

The negative refraction achieved by the teams at Berkeley would be different.

"Instead of the fish appearing to be slightly ahead of where it is in the water, it would actually appear to be above the water's surface," Valentine said. "It's kind of weird."

For a metamaterial to produce negative refraction, it must have a structural array smaller than the wavelength of the electromagnetic radiation being used. This was done using microwaves in 2006 by David Smith of Duke University in North Carolina and John Pendry of Imperial College London.

Visible light is harder. Some groups managed it with very thin layers, virtually only one atom thick, but these materials were not practical to work with and absorbed a great deal of the light directed at it.

"What we have done is taken that material and made it much thicker," Valentine said.

His team, whose work is reported in Nature, used stacked silver and metal dielectric layers stacked on top of each other and then punched through with holes. "We call it a fishnet," Valentine said.

The other team, reporting in Science, used an oxide template and grew silver nanowires inside porous aluminum oxide at tiny distances apart, smaller than the wavelength of visible light. This material refracts visible light.

Immediate applications might be superior optical devices, Valentine said -- perhaps a microscope that could see a living virus.

"However, cloaking may be something that this material could be used for in the future," he said. "You'd have to wrap whatever you wanted to cloak in the material. It would just send light around. By sending light around the object that is to be cloaked, you don't see it."

Very cool! Maybe I could wrap my MB?

__________________
1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

That would be one hell of a paint job. Probably look like "Predator".

On a related subject, have you (and anybody) ever heard of those (illegal) broadcasting devices that automagically hang-up everybody's cellphone within a few dozen feet of the antenna? How complicated are they to build?

Not very hard.

http://projects2.gbppr.org/mil/celljam

Yes supposidly a member on here may know or have seen one at some point.

You can purchase them online, but I wouldn't recomend it since breaking the law is bad!

__________________
1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Ah! Those bastards put it on the web! How insensitive to the people who need to text or talk while they put on make-up or wander into other lanes of traffic.

B

I wonder if the same company makes this that I ordered my Star-Trek food replicator from a convention in the 80's.

Science closing in on cloak of invisibility
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Thu Jan 15, 3:21 pm ET

WASHINGTON – They can't match Harry Potter yet, but scientists are moving closer to creating a real cloak of invisibility.

Researchers at Duke University, who developed a material that can "cloak" an item from detection by microwaves, report that they have expanded the number of wavelengths they can block.

In 2006 the team reported they had developed so-called metamaterials that could deflect microwaves around a three-dimensional object, essentially making it invisible to the waves.

The system works like a mirage, where heat causes the bending of light rays and cloaks the road ahead behind an image of the sky.

The researchers report in Thursday's edition of the journal Science that they have developed a series of mathematical commands to guide the development of more types of metamaterials to cloak objects from an increasing range of electromagnetic waves.

"The new device can cloak a much wider spectrum of waves — nearly limitless — and will scale far more easily to infrared and visible light. The approach we used should help us expand and improve our abilities to cloak different types of waves," senior researcher David R. Smith said in a statement.

The new cloak is made up of more than 10,000 individual pieces of fiberglass arranged in parallel rows. The mathematical formulas are used to determine the shape and placement of each piece to deflect the electromagnetic waves.

The research was supported by Raytheon Missile Systems, the Air Force Office of Scientific Research, InnovateHan Technology, the National Science Foundation of China, the National Basic Research Program of China and National Science Foundation of Jiangsu Province, China.