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Metamaterials: a real invisibility cloak

if I ever get one I'm gonna tape some untasteful things to the small camera to project all over my vehicle. Great tech; and I cannot wait to trial it one day!!
 
According to some conspiracy theory advocates, the technology has been in use for years now.

Opps, I've said too much, gotta go, the black helos are here. :Tin-Foil-Hat:
 
cupper said:
According to some conspiracy theory advocates, the technology has been in use for years now.

Opps, I've said too much, gotta go, the black helos are here. :Tin-Foil-Hat:

I'm pretty sure we already have the technology in the CF. We have loads of AFVs, helicopters, ships and soldiers....you just can't see them!
 
Not to be confused with technologies to cloak objects in the infra-red spectrum:
http://www.wired.com/dangerroom/2011/09/invisibility-cloak-tanks-cows/?utm_source=Contextly&utm_medium=RelatedLinks&utm_campaign=Previous

...or technology to cloak objects in the visible light spectrum, aka mirage cloaking:
http://www.wired.com/dangerroom/2011/10/invisibility-cloak-mirage/

I can see future armor combining several upcoming technologies to shield us from prying eyes, and electronic detection.  Starcraft 'ghost' unit anyone?  :nod:
 
Should be joined to this thread: Metamaterials: a real invisibility cloak http://forums.army.ca/forums/threads/50470/post-446595.html#msg446595
 
Bah, that's nothing, I have known several Gunners and Bombadiers that perfected vanishing to an art form, You would see them in the morning and then at the end of the day.
 
Thucydides said:
Should be joined to this thread: Metamaterials: a real invisibility cloak http://forums.army.ca/forums/threads/50470/post-446595.html#msg446595

Agreed.  One stop shopping for all things invisible (a serious conversation on my work ethic could fit in here).  As an aside, your original thread didn't pop up on my search for 'cloaking device'.
 
Further advances in cloaking technologies:

http://iopscience.iop.org/1367-2630/14/1/013054/pdf/1367-2630_14_1_013054.pdf

http://nextbigfuture.com/2012/01/experimental-verification-of-three.html

Three-dimensional plasmonic cloak hides a cylinder from microwaves
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New Journal of Physics - Experimental verification of three-dimensional plasmonic cloaking in free-space (14 pages) They optimized the cloak design for the 3 GHz range. They have hidden a cylinder from microwaves, demonstrating cloaking of an object in free space, rather than a two-dimensional image. The group has not been able to scatter visible light, but it expects that cloaking small objects is possible. The results pave the way to realistic, practical applications of 3D stand-alone cloaks for radar evasion and non-invasive radio frequency probing.

BBC News - The approach used is unlikely to work at the visible light part of the spectrum. Prof Alu explained that the approach could be applied to the tips of scanning microscopes - the most high-resolution microscopes science has - to yield an improved view of even smaller wavelengths of light.

In future applications, plasmonic materials could be combined with the structured metamaterials idea already in development elsewhere. Light can be channelled where it needs to go, or its effects undone, as need be.

Prof Apu said that if he had to bet in five years what kind of cloaking technique might be used for applications, for practical purposes, then he would say plasmonic cloaking is a good bet.

We report the experimental verification of metamaterial cloaking for a 3D object in free space. We apply the plasmonic cloaking technique, based on scattering cancellation, to suppress microwave scattering from a finite-length dielectric cylinder. We verify that scattering suppression is obtained all around the object in the near- and far-field and for different incidence angles, validating our measurements with analytical results and full-wave simulations. Our nearfield and far-field measurements confirm that realistic and robust plasmonic metamaterial cloaks may be realized for elongated 3D objects with moderate transverse cross-section at microwave frequencies.
 
All the invisibility posts are now here, merged.

Milnet.ca Staff
 
Colin P said:
Bah, that's nothing, I have known several Gunners and Bombadiers that perfected vanishing to an art form, You would see them in the morning and then at the end of the day.
Same for some officers.
 
milnews.ca said:
All the invisibility posts are now here, merged.

Milnet.ca Staff

If they are invisible, how are we going to read them? ;)
 
Low cost metamaterials are within reach. Once it becomes practical to make this in bulk many exciting possibilities open up:

http://oregonstate.edu/ua/ncs/archives/2012/feb/discovery-opens-avenue-“negative-refraction”-new-products-and-industries

“NEGATIVE REFRACTION” OPENS AVENUE TO NEW PRODUCTS AND INDUSTRIES

CORVALLIS, Ore. – Researchers at Oregon State University have discovered a way to make a low-cost material that might accomplish negative refraction of light and other radiation – a goal first theorized in 1861 by a giant of science, Scottish physicist James Maxwell, that has still eluded wide practical use.

Other materials can do this but they are based on costly, complex crystalline materials. A low-cost way that yields the same result will have extraordinary possibilities, experts say – ranging from a “super lens” to energy harvesting, machine vision or “stealth” coatings for seeming invisibility.

Entire new products and industries could be possible. The findings have just been published and a patent has been applied for on the technology.

The new approach uses ultra-thin, ultra-smooth, all-amorphous laminates, essentially a layered glass that has no crystal structure. It is, the researchers say, a “very high-tech sandwich.”

The goal is to make radiation bend opposite to the way it does when passing through any naturally occurring material. This is possible in theory, as Maxwell penciled out during the American Civil War. In reality, it’s been pretty difficult to do.

“To accomplish the task of negative refraction, these metamaterials have to be absolutely perfect, just flawless,” said Bill Cowell, a doctoral candidate in the OSU School of Electrical Engineering and Computer Science. “Everyone thought the only way to do that was with perfectly crystalline materials, which are quite expensive to produce and aren’t very practical for large-area commercial application.

“We now know these materials may not need to be that exotic.”

The new study has explained how easy-to-produce laminate materials, created with technology similar to that used to produce a flat panel television, should work for this purpose. The findings outline the component materials and the theoretical behavior of the laminates, Cowell said. They were just published in Physica Status Solidi A, in work supported by the National Science Foundation.

“We haven’t yet used this approach to achieve negative refraction, but the findings suggest it should work for that,” he said. “That will be one goal of continuing research. No one had thought of using amorphous metals for this purpose. They didn’t think it could be that simple.”

Negative refraction, Cowell said, is a brilliant idea. It is based on the equations developed by the young physicist and mathematician Maxwell more than 150 years ago – work for which he is revered, along with Isaac Newton and Albert Einstein, as one of the greatest physicists who ever lived. Einstein kept a photograph of Maxwell on his office wall.

But for generations, theory is about all that it was. Just in the past decade have researchers finally figured out how to create materials of any type that can achieve negative refraction. A way to accomplish that at low cost for the commercial marketplace could be of considerable importance, scientists say.

One application of particular interest is a “super lens,” a device that might provide light magnification at levels that dwarf any existing technology. Many applications are possible in electronics manufacturing, lithography, biomedicine, insulating coatings, heat transfer, space applications, and perhaps new approaches to optical computing and energy harvesting.

The discovery of amorphous metamaterials is an outgrowth of recent findings at OSU about ways to create a metal-insulator-metal, or MIM diode, also of commercial significance. The OSU research is one of the latest advances in “dispersion engineering,” or the control of electromagnetic radiation.

About the OSU College of Engineering: The OSU College of Engineering is among the nation’s largest and most productive engineering programs. In the past six years, the College has more than doubled its research expenditures to $27.5 million by emphasizing highly collaborative research that solves global problems, spins out new companies, and produces opportunity for students through hands-on learning.

The "other" applications of metamaterials such as super lenses and energy harvesting have applications on the military side as well; high power optics that are much smaller and lighter than existing ones, and the ability to concentrate solar energy to make small man portable collectors that can generate useful amounts of energy when the sun is shining come to mind.
 
Another group of scientists discovers a simpler method of achievig the effects of metamaterials. Since both metamaterials and this technique uses material science properties to refract the incoming waves in the direction the designers choose, this can be literally "bolted on" to existing vehicles, buildings etc:

http://nextbigfuture.com/2013/09/shaped-teflon-can-hide-objects-from.html

Shaped teflon can hide objects from microwaves from one direction

Look out for mass-produced invisibility cloaks thanks to an entirely new way of designing and manufacturing them out of materials such as Teflon. The new approach is to create a computer model of the cloak in the form of a conventional material with fixed light bending properties. The model simulates how this conventional material distorts light as it passes by. The computer then changes the shape and topology of the material to reduce this distortion. By repeating this process many times, it is possible to find a topology that minimises the distortion of light so that it remains more or less unchanged as it passes by. The result is an invisibility cloak; not a perfect one but one that can hold its own against many of those made of metamaterials.

Today, Lu Lan at Zhejiang University in China and a few pals have actually created the first invisibility cloak designed using topology optimisation. They carved it out of Teflon and it took them all of 15 minutes using a computer-controlled engraving machine. “The fabrication process of a sample is substantially simplified,” they say.

The resulting “Teflon eyelid” invisibility cloak hides a cylindrical disc of metal the size of poker chip from microwaves. But crucially, its performance closely matches the prediction of the computer simulation

The same approach can work in optical wavelengths. “Such a cloaking setup won’t be a big problem to replicate in the THz or even optical spectrum,” they say.

Next the researchers want to develop the technique to create cloaks that work over a range of frequencies and at a range of angles.
 
Interesting,  can see the application of this on the upper works of ships, to reduce both the radar and visual signature. As Radar is technical LOS, cloaking the upper works would reduce the "visible" range that you would be spotted, combined with low signature construction, you may have a very hard to detect ship.
 
U of T discovers yet another way to bend radiiation around an object. there are multiple means to achieve invisibility now, the real question is becoming which one is most robust and cost effective for a particular application?

http://media.utoronto.ca/media-releases/thin-active-invisibility-cloak-demonstrated-for-first-time/

Thin, active invisibility cloak demonstrated for first time
Posted on November 12, 2013
TORONTO, ON — Invisibility cloaking is no longer the stuff of science fiction: two researchers in The Edward S. Rogers Sr. Department of Electrical & Computer Engineering have demonstrated an effective invisibility cloak that is thin, scalable and adaptive to different types and sizes of objects.

Professor George Eleftheriades and PhD student Michael Selvanayagam have designed and tested a new approach to cloaking—by surrounding an object with small antennas that collectively radiate an electromagnetic field. The radiated field cancels out any waves scattering off the cloaked object. Their paper ‘Experimental demonstration of active electromagnetic cloaking’ appears today in the journal Physical Review X.

“We’ve taken an electrical engineering approach, but that’s what we are excited about,” says Eleftheriades. “It’s very practical.”

Picture a mailbox sitting on the street. When light hits the mailbox and bounces back into your eyes, you see the mailbox. When radio waves hit the mailbox and bounce back to your radar detector, you detect the mailbox. Eleftheriades and Selvanyagam’s system wraps the mailbox in a layer of tiny antennas that radiate a field away from the box, cancelling out any waves that would bounce back. In this way, the mailbox becomes undetectable to radar.

“We’ve demonstrated a different way of doing it,” says Eleftheriades. “It’s very simple: instead of surrounding what you’re trying to cloak with a thick metamaterial shell, we surround it with one layer of tiny antennas, and this layer radiates back a field that cancels the reflections from the object.”

Their experimental demonstration effectively cloaked a metal cylinder from radio waves using one layer of loop antennas. The system can be scaled up to cloak larger objects using more loops, and Eleftheriades says the loops could become printed and flat, like a blanket or skin. Currently the antenna loops must be manually attuned to the electromagnetic frequency they need to cancel, but in future they could function both as sensors and active antennas, adjusting to different waves in real time, much like the technology behind noise-cancelling headphones.

Work on developing a functional invisibility cloak began around 2006, but early systems were necessarily large and clunky—if you wanted to cloak a car, for example, in practice you would have to completely envelop the vehicle in many layers of metamaterials in order to effectively “shield” it from electromagnetic radiation. The sheer size and inflexibility of the approach makes it impractical for real-world uses.  Earlier attempts to make thin cloaks were not adaptive and active, and could work only for specific small objects.

Beyond obvious applications, such as hiding military vehicles or conducting surveillance operations, this cloaking technology could eliminate obstacles—for example, structures interrupting signals from cellular base stations could be cloaked to allow signals to pass by freely. The system can also alter the signature of a cloaked object, making it appear bigger, smaller, or even shifting it in space. And though their tests showed the cloaking system works with radio waves, re-tuning it to work with Terahertz (T-rays) or light waves could use the same principle as the necessary antenna technology matures.

“There are more applications for radio than for light,” says Eleftheriades. “It’s just a matter of technology—you can use the same principle for light, and the corresponding antenna technology is a very hot area of research.”

-30-

For more information, contact:

Marit Mitchell
Senior Communications Officer
The Edward S. Rogers Sr. Department of Electrical & Computer Engineering
Tel: 416-978-7997
marit.mitchell@utoronto.ca
 
More on using these techniques to bend sound. Soon these techniques may have advanced to the point that they can be applied to ships and submarines as well:

http://www.pratt.duke.edu/news/acoustic-cloaking-device-hides-objects-sound

Acoustic Cloaking Device Hides Objects from Sound
March 11, 2014
Duke engineers build world’s first 3-D acoustic cloaking device
By Ken Kingery

Using little more than a few perforated sheets of plastic and a staggering amount of number crunching, Duke engineers have demonstrated the world’s first three-dimensional acoustic cloak. The new device reroutes sound waves to create the impression that both the cloak and anything beneath it are not there.

The acoustic cloaking device works in all three dimensions, no matter which direction the sound is coming from or where the observer is located, and holds potential for future applications such as sonar avoidance and architectural acoustics.

The study appears online in Nature Materials.

Bogdan Popa, a research scientist in electrical and computer engineering, shows off the 3D acoustic cloak he helped design and build as a member of Steven Cummer’s laboratory.

“The particular trick we’re performing is hiding an object from sound waves,” said Steven Cummer, professor of electrical and computer engineering at Duke University. “By placing this cloak around an object, the sound waves behave like there is nothing more than a flat surface in their path.”

To achieve this new trick, Cummer and his colleagues turned to the developing field of metamaterials—the combination of natural materials in repeating patterns to achieve unnatural properties. In the case of the new acoustic cloak, the materials manipulating the behavior of sound waves are simply plastic and air. Once constructed, the device looks like several plastic plates with a repeating pattern of holes poked through them stacked on top of one another to form a sort of pyramid.

A close up view of the 3D acoustic cloak. The geometry of the plastic sheets and placement of the holes interacts with sound waves to make it appear as if it isn’t there.

To give the illusion that it isn’t there, the cloak must alter the waves’ trajectory to match what they would look like had they had reflected off a flat surface. Because the sound is not reaching the surface beneath, it is traveling a shorter distance and its speed must be slowed to compensate.
“The structure that we built might look really simple,” said Cummer. “But I promise you that it’s a lot more difficult and interesting than it looks. We put a lot of energy into calculating how sound waves would interact with it. We didn’t come up with this overnight.”

To test the cloaking device, researchers covered a small sphere with the cloak and “pinged” it with short bursts of sound from various angles. Using a microphone, they mapped how the waves responded and produced videos of them traveling through the air.

Cummer and his team then compared the videos to those created with both an unobstructed flat surface and an uncloaked sphere blocking the way. The results clearly show that the cloaking device makes it appear as though the sound waves reflected off an empty surface.

Although the experiment is a simple demonstration showing that the technology is possible and concealing an evil super-genius’ underwater lair is a long ways away, Cummer believes that the technique has several potential commercial applications.

“We conducted our tests in the air, but sound waves behave similarly underwater, so one obvious potential use is sonar avoidance,” said Cummer. “But there’s also the design of auditoriums or concert halls—any space where you need to control the acoustics. If you had to put a beam somewhere for structural reasons that was going to mess up the sound, perhaps you could fix the acoustics by cloaking it.”

This research was supported by Multidisciplinary University Research Initiative grants from the Office of Naval Research (N00014-13-1-0631) and from the Army Research Office (W911NF-09-1-00539).

###

“Three-dimensional broadband omnidirectional acoustic ground cloak,” Zigoneanu L., Popa, B., Cummer, S.A. Nature Materials, March 9, 2014. DOI: 10.1038/NMAT3901
 
More advances in metamaterial technologies:

http://today.ucf.edu/nanotech-leads-break-stealth-technology/

NanoTech Leads to Break-Through in Stealth Technology

Controlling and bending light around an object so it appears invisible to the naked eye is the theory behind fictional invisibility cloaks.

It may seem easy in Hollywood movies, but is hard to create in real life because no material in nature has the properties necessary to bend light in such a way. Scientists have managed to create artificial nanostructures that can do the job, called metamaterials. But the challenge has been making enough of the material to turn science fiction into a practical reality.

The work of Debashis Chanda at the University of Central Florida, however, may have just cracked that barrier. The cover story in the March edition of the journal Advanced Optical Materials, explains how Chanda and fellow optical and nanotech experts were able to develop a larger swath of multilayer 3-D metamaterial operating in the visible spectral range. They accomplished this feat by using nanotransfer printing, which can potentially be engineered to modify surrounding refractive index needed for controlling propagation of light.

“Such large-area fabrication of metamaterials following a simple printing technique will enable realization of novel devices based on engineered optical responses at the nanoscale,” said Chanda, an assistant professor at UCF.

The nanotransfer printing technique creates metal/dielectric composite films, which are stacked together in a 3-D architecture with nanoscale patterns for operation in the visible spectral range. Control of electromagnetic resonances over the 3-D space by structural manipulation allows precise control over propagation of light. Following this technique, larger pieces of this special material can be created, which were previously limited to micron-scale size.

By improving the technique, the team hopes to be able to create larger pieces of the material with engineered optical properties, which would make it practical to produce for real-life device applications. For example, the team could develop large-area metamaterial absorbers, which would enable fighter jets to remain invisible from detection systems.

Other members of the research team include: Li Gao, Youngmin Kim, Kazuki Shigeta, Steven Hartanto and John Rogers from the University of Illinois at Urbana-Champaign; Abraham Vasquez-Guardado and Daniel Franklin from UCF: Christopher J. Progler from Photronics Inc. and Gregory R. Bogart from the Sandia National Laboratories.

Chanda joined UCF in Fall 2012 from University of Illinois at Urbana-Champaign with joint appointment with the Nanoscience Technology Center and the College of Optics and Photonics (CREOL). He has published multiple articles on light-matter interactions and metamaterials and is a reviewer for multiple journals in his field. For some of his pioneering works, Debashis was awarded a Department of Energy solar innovation award and a Natural Sciences and Engineering Research Council award among others. He also earned a National Science Foundation Summer Institute Fellowship in 2013.
 
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