Step aside, Harry Potter. There's a new invisibility cloak in town, and while it's still far from being practical, it may one day help you evade detection — no magic necessary.
That's the news out of the journal Science this week. Researchers from the University of California, Berkeley have developed a new type of super-thin, skin-like "metasurface" that is capable of making small objects disappear.
While it's not yet ready to disguise humans — sorry, hide-and-seekers — this is the closest scientists have come to creating an actual garment that can hide objects from prying eyes.
It's just a little bit too small for anyone to wear just yet.
The concept of making real invisibility cloaks has been around since 2006. Scientists have been developing "metamaterials" with special mathematical and electromagnetic properties that can trick your eyes into believing something isn't there.
There are various prototypes that cloak objects in different ways — some can be fashioned out of extremely thin wires made of silica and gold, carbon fibers, silk, or a series of lenses — but the most promising technique involves manipulating light.
When you look at an apple, you can tell that it's red because the fruit absorbs all wavelengths of visible light except for wavelengths associated with the color red. That wavelength bounces off of the fruit and into your eye, where it is then processed by your brain.
That's how vision works.
To trick your vision, an invisibility cloak would have to stop light from bouncing off objects and back to your eye. Some do this by making the wavelengths of light bypass the object.
In a similar way that water flows around a boulder in a river, scientists are using special materials to create cloaks that can reroute wavelengths of light around the edges of an object instead of deflecting them back into your eye. This tricks your brain into thinking the object isn't there.
In the past, cloaking prototypes have been big and bulky, and generally much larger than the objects they were trying to mask. They were "less like Harry Potter's cloak and more like Harry Potter's shed," John Pendry, a theorist at Imperial College London who first introduced the idea of a cloak in 2006, told Science Magazine.
The new cloak announced this week doesn't bend light waves around an object, but reflects and reroutes a distorted version of those wavelengths, thus rendering them — and the object — undetectable.
The new skin-tight "metasurface" is made of a super-thin insulator material speckled with gold rectangles that absorb and then re-radiate light waves in a way that your eyes can't recognize. The material is less than a micrometer thick — a fraction of the size of a human cell — and can be wrapped around objects like a skin.
Here's what it looks like, in an artist's conception from the paper:
One advantage of the cloak, according to a press release, is that it can conceal objects with sharp peaks and edges, which has proven extremely challenging with cloaks in the past.
But many limitations remain. Scientists have currently only tested the cloak on microscopic objects already invisible to the naked eye — which sort of negates the need for an invisibility cloak in the first place. But with more research, the cloak could eventually be scaled up to hide larger objects, the researchers say.
There's also an issue with movement. As reported by Science Magazine, the gold rectangles sitting on the surface of the material have to line up just right with the object the material is trying to conceal. If that object is a person, the cloak will no longer work once the person moves.
Nevertheless, though, researchers are excited about this new surface. It could eventually open doors to new exciting applications, such as a skin that could make a fighter jet appear to be a freight plane on radar.
"It really proves the power of the metasurface concept," Andrea Alú, an electrical engineer at the University of Texas, Austin, who was not affiliated with the study, told Science Magazine. "It's a great result."
