Copper-based screen cloaks objects from microwaves

Researchers have developed a cloak that is micrometres thick and can hide 3D objects from microwaves in their natural environment, in all directions and from all of the observers’ positions.

The development is claimed to be an advance on previous attempts at so-called cloaking devices that have been bulky.

Presenting their study today, 26 March, in the Institute of Physics and German Physical Society’s 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 66µm-thick copper tape to a 100µm-thick, flexible polycarbonate film in a fishnet design. It was used to cloak an 18cm cylindrical rod from microwaves and is said to have shown optimal functionality when the microwaves were at a frequency of 3.6GHz and over a moderately broad bandwidth.

The researchers also predict that due to the inherent conformability (bendiness) of the metascreen and the robustness 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, x-rays or microwaves – rebound off its surface.

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 Prof Andrea Alu in a statement.

‘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.

The paper can be downloaded here.