Smart sunglasses change color almost instantly....watch it

A pair of glasses with lenses that can be transparent or dark, and in shades of yellow, green or purple, all basically at the push of a button.

Chemists at the University of Washington in Seattle say they are developing ‘smart' sunglasses that will let the wearer instantly change the color of their lenses to virtually any hue of the rainbow. So, whether you like your lenses clear, red, green, blue or purple, virtually any color could be obtained instantly by tuning a tiny electronic knob in the frame, the researchers said in a release.

The prototype glasses are powered by a watch battery that attaches to the glasses frame, and the wearer spins a tiny dial on the arm of the glasses to change color. The lenses were created by sandwiching a gel between two layers of electrochromic material. Applying a small voltage moves charged particles from one layer to another, and changes the transparency. Once the glasses are a certain tint they will stay that way without power for about 30 days. A single watch battery is able to power thousands of transitions, said Chunye Xu, research assistant professor of mechanical engineering at the University of Washington in the statement.

Motorcyclists, skiers or mountain bikers might be in the shade one moment and pop into bright sunlight an instant later. Some high-end sunglasses already let athletes adjust to such changing conditions by swapping out lenses. But the new shades, which take from one to two seconds to transition, allow a much quicker switch, researchers said. Current lens choices don't simply include different levels of shading, but also different colors, such as yellow lenses, said to enhance contrasts and improve depth perception, or rose-colored glasses, which brighten low-light scenes. The new glasses would offer an endless range of options on one accessory, the release said. Doctors already are recommending sunglasses that darken in response to the lighting conditions, known as photochromic lenses. These use incoming UV rays to trigger a chemical reaction that darkens the lens, but users can't adjust the shade.

Also, the lenses may stay bright under strong midday light or get too dark in low-level evening light due to the angle of incoming rays. And photochromic lenses have the drawback that when behind a UV-protected surface, such as a car's window, the glasses won't change color. Adjustable lenses would avoid that problem. Researchers made the glasses using electrochromic materials that change transparency depending on the electric current.

The UW glasses are based on a new type of smart window using organic, rather than inorganic, oxides.