From Chicago, at the American Chemical Society Meeting
Some people want their sunglasses dark green. Others prefer brown or deep-blue shades. Engineers have developed a way to change eyewear lenses from blue back to clear—at the flip of a switch. Future glasses may switch among any of a series of colors.
The changeable shades rely on novel polymer films sandwiched between layers of glass. Depressing a switch on the frames sends a tiny current from a watch battery to the polymer in each lens. Applying the current once turns this electrochromic polymer a dark color. Hit the switch again and the color goes away. Once the film becomes transparent or assumes a color, it needs no further power to stay that way—at least for 30 days.