Engineers Improve Real-Life Cloaking Technology

• By Dian Schaffhauser
• 01/26/09

A team of Duke University engineers is working on a new type of cloaking device that can bestow invisibility to an object by "cloaking" it from visual light. First prototyped in 2006, the newest version can cloak in a broader range of frequencies than an earlier effort.

Cloaking devices bend electromagnetic waves, such as light, in such a way that it appears as if the cloaked object is not there. In the latest laboratory experiments, a beam of microwaves aimed through the cloaking device at a "bump" on a flat mirror surface bounced off the surface at the same angle as if the bump weren't present.

The latest advance was made possible by the development of a new series of algorithms, to guide the design and fabrication of exotic composite materials known as metamaterials. These materials can be engineered to have properties not easily found in natural materials, and can be used to form a variety of "cloaking" structures. These structures can guide electromagnetic waves around an object, only to have them emerge on the other side as if they had passed through an empty volume of space.

The results of the latest Duke experiments were published in Science by Duke's Ruopeng Liu, who developed the algorithm, and Chunlin Ji.

"The difference between the original device and the latest model is like night and day," said David Smith, professor of electrical and computer engineering at Duke and the senior member of the research team. "The new device can cloak a much wider spectrum of waves--nearly limitless--and will scale far more easily to infrared and visible light. The approach we used should help us expand and improve our abilities to cloak different types of waves."

Smith said that cloaks should find numerous applications as the technology is perfected. By eliminating the effects of obstructions, cloaking devices could improve wireless communications, or acoustic cloaks could serve as protective shields, preventing the penetration of vibrations, sound, or seismic waves.

The newest cloak, which measures 20 inches by 4 inches and less than an inch high, is actually made up of more than 10,000 individual pieces arranged in parallel rows. Of those pieces, more than 6,000 are unique. Each piece is made of the same fiberglass material used in circuit boards and etched with copper.

The algorithm determined the shape and placement of each piece. Without the algorithm, properly designing and aligning the pieces would have been extremely difficult, Smith said.

The research was supported by both American and Chinese organizations, including Raytheon Missile Systems, the Air Force Office of Scientific Research, China firm InnovateHan Technology, the National Science Foundation of China, the National Basic Research Program of China, and the National Science Foundation of Jiangsu Province.