Personal invisibility cloaks are within reach — a pioneering electrical engineer promises that anyone with access to a 3-D printer "can literally make a plastic cloak overnight" that masks small objects under specific wavelengths of light.

Invisibility cloaks have long been the stuff of fiction, from ancient Greek mythology to Harry Potter. In recent years, engineering advances have brought the magical devices into the realm of scientific possibility.

In 2006, a team of engineers at Duke University developed the first working invisibility cloak. The metamaterial device was limited — it only worked in two dimensions under microwave beams, not visible light. Since then, researchers have further developed the technology to cloak three-dimensional objects as large as one foot in diameter, with no telltale shadows.

Now Yaroslav Urzhumov, an assistant research professor in electrical and computer engineering at Duke University, has announced a design for such a device in the journal Optics Letters that is so simple to reproduce that anyone with access to a standard 3-D printer can build their own.

How Does the Invisibility Cloak Work?

Invisibility cloak technology still only deflects microwave beams, but the researchers are hopeful that they can eventually tweak their technique to ward off higher wavelengths like visible and infrared light, for true optical invisibility to the human eye.

Yaroslav Urzhumov shows off the 3D-printed invisibility cloaking device, Frisbee-sized and punctured throughout with microwave-deflecting holes. [Duke University]

Urzhumov's cloaking device is a round disk the size of a Frisbee, punctured with holes of various shapes and sizes that are designed to deflect microwave beams. An opaque object is placed in a round open area in the center of the disk, and when microwave beams are projected at the object, the cloak's design wards off the beams so the object appears invisible.

"The design of the cloak eliminates the 'shadow' that would be cast, and suppresses the scattering from the object that would be expected," explained Urzhumov in a news release.

"In effect, the bright, highly reflective object, like a metal cylinder, is made invisible. The microwaves are carefully guided by a thin dielectric shell and then re-radiated back into free space on the shadow side of the cloak."

David Smith, Duke engineering professor and senior author on the new paper, explained the science of invisibility-promoting metamerials last year:

How Can You Print Your Own Cloaking Device?

Urzhumov says that anyone who can afford a standard three-dimensional printer can make their own version of the invisibility cloaking device at home, printing it from plastic polymers in only three to seven hours.

3-D printing, also known as additive manufacturing, uses a moving nozzle that lays down successive layers of material, usually moldable plastic, according to a digital blueprint.

3-D printers are now commercially available for several thousand dollars, and are already revolutionizing biotechnology with advances like 3-D printed artificial cell membranes, bionic ears, skull implants, anatomical models of X-rays and ultrasounds, bio-bots, and even medications.

Future Directions for Invisibility Technology

With nanotechnology, Urzhumov says that 3D printers can build invisibility cloaking devices out of transparent plastic or glass, which in theory can deflect microwave beams as effectively as the opaque plastic polymer he used. If that works, the cloaking device itself would be hard to see with the naked eye.

While the existing technology can't cloak objects much larger than a foot-long cylinder, Urzhumov believes that scaled-up cloaking devices can make much larger objects invisible.

"Computer simulations make me believe that it is possible to create a similar polymer-based cloaking layer as thin as one inch wrapped around a massive object several meters in diameter," he said in the news release.

Urzhumov's invisibility cloak may not be quite as functional as Harry Potter's, but the ability to mass produce such a device with a 3D printer sets a tantalizing precedent.

If and when researchers develop larger invisibility cloaks that can deflect visible light from moving objects, it's easy to imagine the fascinating — and unnerving — possibility that anyone could print one in their basement and wander around unseen.

The full paper on the 3-D printed microwave invisibility cloaking device is published online in the journal Optics Letters.