University Researchers Posit Theoretical Blueprint for Invisibility Cloak

It may seem like something out of a "Harry Potter" novel, but the schoolboy wizard in this tale is nowhere to be found. Rather, physicists at Duke University's Pratt School of Engineering and Imperial College London are responsible for the illusion.

Three physicists say they have developed the blueprint for an "invisibility cloak," or fabric, to make physical objects appear as though they have disappeared when they are covered.

The key to making the cloak work comes from an exotic artificial composite called "metamaterials," which could have numerous uses, from defense applications to wireless communications, according to David R. Smith, professor of electrical and computer engineering at Duke's Pratt School.

Smith, along with Duke's Pratt School doctorial candidate David Schurig, and Imperial College London's John Pendry, presented the theoretical papers, on Thursday. It appeared in Science Express, an online science journal. The United States Defense Advanced Research Projects Agency (DARPA) supported the work.

"The ability to hide or conceal things electromagnetically is a method used to design electromagnetic structures," Smith said. "We've been working on the project for about one year, and would have only been considered practical recently. It's been made possible by metamaterials because it can literally transform space, which is difficult to do with conventional material."The cloak works on the principal of light as an electromagnetic wave, with a longer wavelength than X-rays and ultraviolet and shorter wavelength than infrared, microwaves and radio waves. The electromagnetic waves follow four mathematical formulas established nearly 150 years ago by James Clerk Maxwell.

Light that transmits through the fabric is made indistinguishable from light that passes through free space. "Using Negative dialectic constant materials is likely in principle, as we are discovering things in small scale that are possible in laborites," said B. Sriram Shastry, physics professor at the University of California at Santa Cruz.

Shastry didn't take part in the project, but said "the things we see in 'Star Trek' are still far beyond what's available to reproduce in the laboratory, but they don't violate any laws of physics as we know it today." In theory, electromagnetic waves would flow around the object covered by the metamaterials similar to water in a river flowing around a smooth rock. The material would act as though a hole opened in space, and light or other electromagnetic waves were swept around the physical object to emerge on the other side as if materials had passed through empty space, Smith said.

The applications for this technology vary. Cloaking could improve wireless communications by eliminating effects from obstructions. An acoustic cloak could serve as a protective shield, preventing the penetration of vibrations, sound or seismic waves, Schurig said. "For the cloak to be effective it would have to completely encompass the object," he said. Schurig has written a computer program to validate the theories. The team's next goal is to physically verify the "invisibility cloak" works.