Color-tunable sunglasses

Science News,  April 14, 2007  

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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.

The prototype switches only between dark blue and clear, reports Chao Ma of the University of Washingtons Center for Intelligent Materials and Systems in Seattle. Adding more colors will require multiple sandwiched polymer films. How dark any polymer becomes will depend on its chemical formula and on the electrical potential applied by the circuit.

The novel lenses could become "the fashion statement of the future" says program leader Chunye Xu.

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