To the untrained eye, they just look like a sheet of grids or squares of geometrically repeating copper wires. Beautiful, to be sure…but technologically brilliant?
Except that they are. These rows and columns of repeating copper configurations are tediously mapped and built to interact with electromagnetic waves in a very particular way.
Let’s say you wanted to build a magnifying sphere that gave you a close-up view of anything placed in its hollow center. First you start with six magnifying glasses configured like the walls of a cube. That might work, except if you were looking at any of the walls from an angle. So you make the magnifying glasses smaller and smaller and put more and more of them together until you get something that looks like a disco ball.
Well, now the magnifying glasses are probably too small to use. Practically speaking, this would never work. But if you can theoretically grasp this concept, then you can start to grasp metamaterials.
The major difference is that glass can focus light, while metamaterials can (theoretically) manipulate any electromagnetic wave on the spectrum in a variety of unnatural ways.
Take, for example, the first cloaking device ever built. It has several layers of concentric metamaterial rings that are scaled and aligned to interact with microwaves. Instead of having them bounce off in random directions, the material carefully directs them around the circle, joining them back together on the other side. So to an observer sitting opposite the microwave source, it appears as though nothing is in the waves’ way.
While very cool, this first attempt at cloaking had a ton of limitations. It only worked in on the plane of the circles—look down from the top or from a 45-degree angle and there’s no effect. And since no microwaves can get to the interior of the shield while being demonstrated properly, that also means whatever is inside can’t see or talk to the outside world using microwaves.
But this was almost a decade ago. In the years since, a lot of research teams across the nation have made a lot of pretty neat advances, and the most recent comes from the lab of Douglas Werner at Penn State.
Instead of creating a rigid 3D structure that completely shields its interior, Werner and postdoctoral fellow Zhi hao Jiang have created a flexible printed sheet that can wrap around any 2D object and create the illusion that it is made of a different material. For example, a typical radio antenna made of a conducting metal could be made to appear that it’s actually a rod of dielectric material like silicon or Teflon.
Why does that matter?
Well, if you’re trying to hide an object from an enemy spy, that probably won’t help you too much. But if you’re trying to hide an antenna from surrounding radio wave interference while still allowing it to function properly, then you’ve hit the jackpot.
Don’t expect to see it on the shelves or in the real world anytime soon, though. The new coating only works for a 20-degree field of view, which might not be all that helpful when there’s electromagnetic interference all around us every day. But it’s a nice step in the right direction, and the field is still less than a decade old.
The study, “Quasi-Three-Dimensional Angle-Tolerant Electromagnetic Illusion Using Ultrathin Metasurface Coatings,” was published in Advanced Functional Materials by Jiang and Werner of Penn State University.