Washington:  Sunglasses that change colours with the ease of a chameleon could become the hottest fashion accessory.

"This is the next big thing for transition lenses," says Greg Sotzing, professor of chemistry at the University of Connecticut College of Liberal Arts and Sciences, who designed them.

The typical material behind a transition lens is what's called a photochromic film, or a sheet of polymers that change colour when sunlight hits them.

Sotzing's new technology does things slightly differently - his electrochromic lenses are controlled by an electric current passing through them when triggered by a stimulus like light, reports the Journal of Materials Chemistry.

"They're like double pane windows with a gap between them," explains Sotzing.

He and his colleagues squirt a mixture of polymers - or as he calls it, "goop" - in between the layers, creating the lens as it hardens, according to a Connecticut statement.

Currently in talks with sunglass manufacturers, Sotzing says that the world of Hollywood could have a market for this technology.

He describes applications he calls "freaky", including colours that move back and forth across the glasses, evoking styles like those sported by Lady Gaga.

Another benefit of this material is that it can change colours as quickly as electricity passes through it - which is virtually instantaneously. This process could be very useful for the military, Sotzing says.

For example, if a person emerges from a dark passageway and into the desert, a lens that would alter its colour instantly to complement the surroundings could mean life or death for some soldiers.

"Right now, soldiers have to physically change the lenses in their goggles," Sotzing says. "This will eliminate that need."

The mixture of polymers used in this lens, says Sotzing, creates less waste and is less expensive to produce than previous mixtures.

(Agencies)