Invisibility’s Next Frontier: Scientists Cloak 3-D Objects

A group of scientists at the University of Texas at Austin have figured out how to “cloak a three-dimensional object standing in free space.” That means the object is invisible, from any angle of observation.

“This object’s invisibility is independent of where the observer is,” Professor Andrea Alu, the study’s co-author, tells Danger Room. “So you’d walk right around it, and never see it.”

Of course, the Pentagon’s been hot on the invisibility trail for years, and for obvious reasons. Invisibility would make plenty of covert operations way easier to execute, not to mention safer for U.S. personnel and deadlier for their foes.

Already, scientists have taken impressive steps forward, and at a freakily fast pace. Researchers in the U.K. have harnessed the mirage effect to mask objects placed behind a device, and Army-backed research is making impressive strides using meta-materials to bend light around objects. Just a few weeks ago, the world’s mind was collectively blown when Pentagon-funded scientists managed to cloak an actual event.

The latest research, published this week in the New Journal of Physics, uses “plasmonic meta-materials” to make an 18-inch cylindrical tube invisible. Put simply: An everyday object is visible because light rays bound off it, hitting our eyes and allowing our brains to process the info. Different cloaking techniques take different approaches to messing with those light rays.

Meta-materials, for one, redirect light to conceal a given object. But that technique makes it hard to render three-dimensional invisibility. The mirage effect relies on a panel of nanotubes that are electrically stimulated, causing them to bend rays of light and hide whatever is behind the panel. Plasmonic meta-materials, on the other hand, actually cancel out the light scattering from an object. So when coated over the cylinder, they block the rays — from every angle — that would ordinarily make that object visible.

It’s an incredible breakthrough, but one that won’t turn soldiers into ghostly GIs just yet. So far, researchers have figured out how to cloak free-standing objects from high-frequency wavelengths, like the microwave spectrum. They’ve still got to tackle the challenge of making a 3-D object invisible at optical wavelengths — what the human eye would be able to see.

“We have some ideas to make it work,” Alu says. “But the human eye is not our priority. Right now, we’re focused on improving biomedical imaging.”