The researchers were able to “hide” a small copper cylinder from a microwave beam, essentially by deflecting the beam and having it meet on the other side of the object.
Like light waves and radar waves, microwaves bounce off of objects and make them visible — in the case of light waves to the naked eye, and in the case of microwaves or radar waves to other detectors.
Researchers David Schurig and David Smith of Duke University used a type of laboratory-made material called metamaterial — in this case made of copper wires patterned onto sheets of fiberglass composite — to make the cloak.
The device, composed of concentric circles of the metamaterial surrounding the copper cylinder, channels the microwaves around the cylinder rather than reflecting them.
“The waves’ movement is similar to river water flowing around a smooth rock,” Schurig said in a press release from the university.
The work, which will appear in Friday’s edition of the journal Science, was funded by the Defense Advanced Research Projects Agency.
The military is interested in the work because of the possibility of hiding planes from radar, according to the Associated Press. Currently available stealth technology reduces the size of the plane visible to radar, making it difficult to track — but not entirely invisible.
The new research also may be a first step toward a device that could actually hide objects from visible light, but the researchers say they are not yet sure when or if that will become possible.
Conceptually, it would be very possible to adapt the technology to visible light, Schurig told the AP. But, he added, from an engineering standpoint it would be difficult.
The cloak must be specifically configured for a particular bandwidth of radiation. Visible light is made up of many different wavelengths, all of which are much smaller than the wavelength of microwaves.
So to make an object disappear from sight, a cloak would have to interact with all of the wavelengths, or colors, at once, Smith said in the press statement. That technology would require more intricate and tiny metamaterials than those that exist now, he said.
Researcher Natalia Litchinitser of the University of Michigan department of electrical engineering told the AP that the work appeared to be the first experimental demonstration of cloaking based on metamaterials.
“Although the invisibility reported in this paper is not perfect, this work provides a proof-of-principle demonstration of the possibility,” she said.