Archive for the ‘invisibility’ Category

By Lee Roop

Scientists in England have made an object disappear using a composite material of nano-sized particles to change the way its surface appears.

It’s not the invisibility cloak from J.K. Rowling’s Harry Potter novels, but reports on the research say it moves the world one step closer.

Here’s the way it worked. Researchers coated a curved surface with a nanocomposite medium with seven distinct layers, each with a different electrical property depending on position. The effect was to “cloak” an object allowing it to appear flat to electromagnetic waves.


The picture at left shows the cloak not in use where the presence of the object along the path of the traveling wave drastically changes its electric field configuration. At right, where the cloak is in action and the nanocomposite has been applied, there is a reduction in the amount of shadowing seen immediately after the object, as well as a noticeable improvement in the reconstruction of wave fronts. (Queen Mary University of London)

“The design is based on transformation optics, a concept behind the invisibility cloak,” said professor and study co-author Yang Hao of Queen Mary University of London’s School of Electronic Engineering and Computer Science.

Scientists see an early use of the coating in changing how antennas are tethered to a platform. It could allow antennas of different shapes and sizes to be attached to a platform without being detectable.

The underlying design approach could be applied to control any kind of electromagnetic surface waves, researchers said.

http://www.al.com/news/huntsville/index.ssf/2016/07/scientists_move_one_step_close.html

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A cloak of invisibility may be common in science fiction but it is not so easy in the real world. New research suggests such a device may be moving closer to reality.

Scientists said on Thursday they have successfully tested an ultra-thin invisibility cloak made of microscopic rectangular gold blocks that, like skin, conform to the shape of an object and can render it undetectable with visible light.

The researchers said while their experiments involved cloaking a miniscule object they believe the technology could be made to conceal larger objects, with military and other possible applications.

The cloak, 80 nanometers in thickness, was wrapped around a three-dimensional object shaped with bumps and dents. The cloak’s surface rerouted light waves scattered from the object to make it invisible to optical detection.

It may take five to 10 years to make the technology practical to use, according to Xiang Zhang, director of the Materials Sciences Division of the U.S. Department of Energy’s Lawrence Berkeley National Laboratory and a professor at the University of California, Berkeley.

“We do not see fundamental roadblocks. But much more work needs to be done,” said Zhang, whose research was published in the journal Science.

The technology involves so-called metamaterials, which possess properties not present in nature. Their surfaces bear features much smaller than the size of a wavelength of light. They redirect incoming light waves, shifting them away from the object being cloaked.

The cloaking “skin” boasts microscopic light-scattering antennae that make light bouncing off an object look as if it were reflected by a flat mirror, rendering the object invisible.

“The fact that we can make a curved surface appear flat also means that we can make it look like anything else. We also can make a flat surface appear curved,” said Penn State University electrical engineering professor Xingjie Ni, the study’s lead author.

The researchers said they overcame two drawbacks of previous experimental microscopic cloaks that were bulkier and harder to “scale up,” or become usable for larger objects.

Ni said the technology eventually could be used for military applications like making large objects like vehicles or aircraft or even individual soldiers “invisible.”

Ni also mentioned some unconventional applications.

How about a cloaking mask for the face? “All the pimples and wrinkles will no longer be visible,” Ni said. How about fashion design? Ni suggested a cloak that “can be made to hide one’s belly.”

http://www.huffingtonpost.com/entry/invisibility-cloak-may-be-moving-closer-to-reality_55febe51e4b0fde8b0ce9afd


Doctoral student Joseph Choi demonstrates a multidirectional ‘perfect paraxial’ cloak using 4 lenses.


Choi uses his hand to further demonstrate his device.


A laser shows the paths that light rays travel through the system, showing regions that can be used for cloaking an object.

Scientists at the University of Rochester have discovered a way to hide large objects from sight using inexpensive and readily available lenses.

Cloaking is the process by which an object becomes hidden from view, while everything else around the cloaked object appears undisturbed.

“A lot of people have worked on a lot of different aspects of optical cloaking for years,” John Howell, a professor of physics at the upstate New York school, said on Friday.

The so-called Rochester Cloak is not really a tangible cloak at all. Rather the device looks like equipment used by an optometrist. When an object is placed behind the layered lenses it seems to disappear.

Previous cloaking methods have been complicated, expensive, and not able to hide objects in three dimensions when viewed at varying angles, they say.

“From what, we know this is the first cloaking device that provides three-dimensional, continuously multidirectional cloaking,” said Joseph Choi, a graduate student who helped develop the method at Rochester, which is renowned for its optical research.

In their tests, the researchers have cloaked a hand, a face, and a ruler – making each object appear “invisible” while the image behind the hidden object remains in view. The implications for the discovery are endless, they say.

“I imagine this could be used to cloak a trailer on the back of a semi-truck so the driver can see directly behind him,” Choi said. “It can be used for surgery, in the military, in interior design, art.”

Howell said the Rochester Cloak, like the fictitious cloak described in the pages of the Harry Potter series, causes no distortion of the background object.

Building the device does not break the bank either. It cost Howell and Choi a little over $US1000 ($1140) in materials to create it and they believe it can be done even cheaper.

Although a patent is pending, they have released simple instructions on how to create a Rochester Cloak at home for under $US100 (114).

There is also a one-minute video about the project on YouTube.

http://www.smh.com.au/technology/sci-tech/scientists-unveil-invisibility-cloak-to-rival-harry-potters-20140927-10n1dp.html

Scientists seem to have unlocked another technology that was only available in fantasy movies.  Physicists at Duke University have announced that they have successfully cloaked an object with “perfect” invisibility, straight out of Harry Potter.

In 2006 David Smith and his colleagues developed a theory called “transformation optics”.  The theory is based on redirecting magnetic fields around an object making it invisible, according to ScienceNOW.

All attempts at testing the theory provided some level of invisibility but it wasn’t until Dr. Smith started experimenting with metamaterials, which are designed to bend light and other radiation around them that they were able to create a Harry Potter style invisibility cloak.

Graduate student Dr. Landy says all earlier versions of a Harry Potter cloak suffered from reflected light.  Landy explained to Phys.org that “it was much like reflections seen on clear glass. The viewer can see through the glass just fine, but at the same time the viewer is aware the glass is present due to light reflected from the surface of the glass.”

The new cloak got around it by reworking the materials.

“Landy’s new microwave cloak is naturally divided into four quadrants, each of which have voids or blind spots at their intersections and corners with each other,”explains io9. “Thus, to avoid the reflectivity problem, Landy was able to correct for it by shifting each strip so that is met its mirror image at each interface.”

Smith said of the research:

“This to our knowledge is the first cloak that really addresses getting the transformation exactly right to get you that perfect invisibility.”