They can't match Harry Potter yet, but scientists at Duke University are moving closer to creating a real cloak of invisibility.

Researchers have developed a material that can "cloak" an item from detection by microwaves. Now they say they've expanded the number of wavelengths they can block.

Last August the team reported they had developed so-called metamaterials that could deflect microwaves around a three-dimensional object. That essentially makes the object 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've developed a series of mathematical commands that could lead to cloaking objects from an increasing range of electromagnetic waves.