They can't match Harry Potter yet, but scientists are moving closer to creating a real cloak of invisibility.
Researchers at Duke University, who developed a material that can "cloak" an item from detection by microwaves, report that they have expanded the number of wavelengths they can block.
In 2006 the team reported they had developed so-called metamaterials that could deflect microwaves around a three-dimensional object, essentially making it invisible to the waves.
The system works like a mirage, where heat causes the bending of light rays and cloaks the road ahead behind an image of the sky.
The researchers report in Thursday's edition of the journal Science that they have developed a series of mathematical commands to guide the development of more types of metamaterials to cloak objects from an increasing range of electromagnetic waves.
"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," senior researcher David R. Smith said in a statement.
The new cloak is made up of more than 10,000 individual pieces of fiberglass arranged in parallel rows. The mathematical formulas are used to determine the shape and placement of each piece to deflect the electromagnetic waves.
The research was supported by Raytheon Missile Systems, the Air Force Office of Scientific Research, InnovateHan Technology, the National Science Foundation of China, the National Basic Research Program of China and National Science Foundation of Jiangsu Province, China.