PORTLAND, Ore. — Duke University took the wraps off invisibility cloaks Thursday (Oct. 19), announcing that researchers managed to cloak a five-inch-square area from microwave detection.

The cloaking technique worked by using a metamaterial as a shield to redirect microwaves around the cloak. Duke researchers said they hope to create invisibility cloaks for other types of electromagnetic radiation, causing even visible light to flow around shielded regions.

"The movement of the [microwaves] is similar to river water flowing around a smooth rock," said David Schurig, a Duke postdoctoral fellow. The "warped 'threads' could not interact with, or 'see,' objects placed inside the resulting hole," he said.

Duke engineers demonstrated that both electrical and magnetic properties of an inhomogeneous composite material could create a variable index-of-refraction material that conceals by preventing electromagnetic energy from entering an area. Light hitting the cloak "flows" around the hidden object and continues on, undistorted, to the other side. The cloak thus neither reflects nor casts a shadow.

The demonstration cloak used an array of copper rings and wires patterned onto fiberglass composite pc-boards. The concentric two-dimensional rings redirected beams of microwave radiation around the region behind the cloak using variations in the shape of the copper elements, the university said.