Wouldn't it be nice to wear sunglasses that change colors according to the weather or to your new skiing suit? According to the American Chemical Society (ACS), scientists at the University of Washington have developed a new lens material that makes this possible. Their 'smart' sunglasses can change color on demand almost instantly. The key to this improved eyewear technology is an electrochromic polymer that has the ability to change levels of darkness and color in the presence of an electric current. By pushing a button on the frame, your glasses will become red, green, blue or virtually any color. Still, you might have to wait a couple of years before buying such sunglasses.
 The two pictures on the left illustrate how these lenses work. These 'smart' sunglasses can be adjusted so the lenses block from 55 percent (top) to 95 percent (bottom) of the incoming rays. (Credit: Chunye Xu, University of Washington). Here is a link to a larger version of these images.
And as you have guessed from the credit listed above, this research work has been led by Chunye Xu, an assistant professor at the University of Washington and associate director of the University’s Center for Intelligent Materials and Systems (CIMS), whose research is focused on Electroactive Polymers [EAP] and EAP based actuators.
In its own news release, the University of Washington (UW) describes how these glasses were made.
Researchers made the glasses using electrochromic materials that change transparency depending on the electric current. Many groups, including the UW, are developing such materials for so-called "smart windows" that could soon be used in energy-efficient homes and offices. Most smart windows use liquid-crystal technology or inorganic oxides. Those materials are expensive to produce and require a constant or frequent injection of power to hold their tint. The UW glasses are based on a new type of smart window using organic, rather than inorganic, oxides. These are cheaper to manufacture and require less power.
So you'll need to have a battery in these glasses. But how long will it last?
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 or shade. 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, Xu said.
Now, when will be able to get these glasses? Not immediately, and not in all colors, as notes the ACS news release.
Fashion-conscience shoppers will have to wait a little while for this latest thing in eyewear: A practical version of the ‘smart’ sunglasses won’t be available to consumers for another one to two years, says Xu, whose lab has filed several patents related to the color-changing glasses. More testing is needed, she notes.
So far, Xu and her associates have produced the electrochromic polymers in red, blue and green. By combining the polymers of different colors into multiple layers and supplying different levels of current from the batteries in the sunglasses, a wide variety of different colors can be produced in the lenses, Xu says.
This research work -- including a prototype -- has been shown on Tuesday at the 233rd National Meeting & Exposition of the American Chemical Society (March 25-29, 2007, Chicago, IL) in one of the sessions focused on Conjugated Oligomers and Polymers. The title of the presentation was "Smart sunglasses and goggles based on electrochromic polymers." Here are two links to the abstract and to the full paper (PDF format, 3 pages).
Sources: American Chemical Society and University of Washington news releases, via EurekAlert!, March 27, 2007; and various websites
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