Beyond possible military applications, it also might have a very practical use by making mobile communications clearer, they said on Thursday.
"Cloaking technology could be used to make obstacles that impede communications signals 'disappear,'" said David Smith of Duke University in North Carolina, who worked on the study published in the journal Science.
Smith was part of the same research team that in 2006 proved such a device was possible.
He said the new material is easier to make and has a far greater bandwidth. It is made from a so-called metamaterial -- an engineered, exotic substance with properties not seen in nature.
Last Mod: 16 Ocak 2009, 14:14
Metamaterials can be used to form a variety of "cloaking" structures that can bend electromagnetic waves such as light around an object, making it appear invisible.
In this case, the material is made from more than 10,000 individual pieces of fiberglass material arranged in parallel rows on a circuit board.
The team, which included Ruopeng Liu of Duke University and T.J. Cui of Southeast University in Nanjing, China, in lab experiments aimed microwaves through the new cloaking material at a bump on a flat mirror surface. That prevented the microwave beams from being scattered and made the surface appear flat.
Smith said the goal was not to make something visible disappear. Cloaking, he said, can occur anywhere on the electromagnetic spectrum.
"Humans 'see' using visible light, which has wavelengths just under a micron (a millionth of a meter). But cell phones and other wireless devices 'see' using light that has a wavelength on the order of many centimeters," Smith said in an e-mail.
He said objects can block the "view" of these devices, making mobile phone communications more difficult.
"You might have two or more antennas trying to 'see' or receive signals, one being blocked by the other," he said. "You could imagine adding cloaks that would make one antenna invisible to the next, so that they no longer interfered."
Smith said the notion of a device that makes objects invisible to people is still a distant concept, but not impossible.
"This latest structure does show clearly there is a potential for cloaking -- in the science fiction sense -- to become science fact at some point," he said.
While the study's funders included Raytheon Missile Systems and the Air Force Office of Scientific Research, Smith said the technology is not intended to replace "stealth" technology.
"Just about all technologies that have any application, naturally have potential in military applications," he said.
"If this has an impact on communications applications, even commercial, those same applications presumably exist in defense contexts."