'Metascreen' forms ultra-thin invisibility cloak

March 25, 2013, Institute of Physics

(Phys.org) —Up until now, the invisibility cloaks put forward by scientists have been fairly bulky contraptions – an obvious flaw for those interested in Harry Potter-style applications.

However, researchers from the US have now developed a cloak that is just micrometres thick and can hide three-dimensional objects from in their natural environment, in all directions and from all of the observers' positions.

Presenting their study today in the New Journal of Physics, the researchers, from the University of Texas at Austin, have used a new, ultrathin layer called a "metascreen".

The metascreen cloak was made by attaching strips of 66 µm-thick copper tape to a 100 µm-thick, flexible polycarbonate film in a fishnet design. It was used to cloak an 18 cm cylindrical rod from microwaves and showed optimal functionality when the microwaves were at a frequency of 3.6 GHz and over a moderately broad bandwidth.

The researchers also predict that due to the inherent conformability of the metascreen and the of the proposed cloaking technique, oddly shaped and asymmetrical objects can be cloaked with the same principles.

Objects are detected when waves – whether they are sound, light, or microwaves – rebound off its surface. The reason we see objects is because bounce off their surface towards our eyes and our eyes are able to process the information.

Whilst previous cloaking studies have used metamaterials to divert, or bend, the incoming waves around an object, this new method, which the researchers dub "mantle cloaking", uses an ultrathin metallic metascreen to cancel out the 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.

"The advantages of the mantle cloaking over existing techniques are its conformability, ease of manufacturing and improved bandwidth. We have shown that you don't need a bulk metamaterial to cancel the scattering from an object – a simple patterned surface that is conformal to the object may be sufficient and, in many regards, even better than a bulk metamaterial."

Last year, the same group of researchers were the first to successfully cloak a 3D object in another paper published in New Journal of Physics, using a method called "plasmonic cloaking", which used more bulky materials to cancel out the scattering of waves.

Moving forward, one of the key challenges for the researchers will be to use "mantle cloaking" to hide an object from visible light.

"In principle this technique could also be used to cloak light," continued Professor 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. However, the size of the objects that can be efficiently cloaked with this method scales with the wavelength of operation, so when applied to optical frequencies we may be able to efficiently stop the scattering of micrometer-sized objects.

"Still, we have envisioned other exciting applications using the mantle cloak and visible light, such as realizing optical nanotags and nanoswitches, and noninvasive sensing devices, which may provide several benefits for biomedical and optical instrumentation."

Explore further: Scientists create first free-standing 3-D cloak

More information: Demonstration of an ultra-low profile cloak for scattering suppression of a finite-length rod in free space, J C Soric et al 2013 New J. Phys. 15 033037, iopscience.iop.org/1367-2630/15/3/033037/article

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2.6 / 5 (7) Mar 25, 2013
They included pictures of the cloaked objects but they are invisible...so, sorry.
1 / 5 (6) Mar 26, 2013
They included pictures of the cloaked objects but they are invisible...so, sorry.

Remind me not to nuke a pizza when you're around, otherwise you will see the toppings because you can see in microwave wavelengths apparently.
not rated yet Mar 26, 2013
It seems like research in metamaterial cloaking is really taking off the last few years. Given the fact we already have this rudimentary knowledge about the possibilty of cloaking 3D objects, wouldn't it make the Zoo hypothesis more probable? Perhaps we're already being observed by a civilization more advanced than us, one that has perfected cloaking and who knows what more.
not rated yet Mar 26, 2013
Could something like this be used to protect astronauts form high energy particle on space craft?
Effectively bending them around the craft?
3.7 / 5 (3) Mar 26, 2013
Could something like this be used to protect astronauts form high energy particle on space craft?

From what the article says, that wouldn't be a good application for this method. The dangerous stuff in space is high frequency, short wavelength, and spacecraft are big.

The useful applictions for this would more likely be shielding individual components in an electronic device from one another. For example, the camera flash in your iPhone will tend to interfere with the other parts. If you design the flash to give off a known frequency, then you can shield the antenna at that frequency without sheilding it from the antena's desired working frequency.

I kinda object to them calling the above device a cloak though. You wouldn't be able to actually see through an object with this on it. It would still cast a shadow. In visible light it should make the object look black and featureless. This thing isn't bending the waves, it's just cancelling them out.
3 / 5 (2) Mar 26, 2013

"Could something like this be used to protect astronauts form high energy particle on space craft?" - ScottB

The current method screens against microwaves because they are long wavelength.

The deBroglie wavelength of a proton is on the order of 10E-14 meters.

The wavelength of Microwaves is on the order of 10E-1 meter.

You would need to find some matter that was denser than protons to use as your cloak.

Good luck with that.

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