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Sunglasses Developed with Adjustable Shade and Color

Photonics Spectra
May 2007
‘Smart’ lenses with chameleon’s powers are driven by electrochromic polymer.

Michael A. Greenwood

Tired of fumbling to find the right eyewear to meet the ever-changing intensity of the sun? Having trouble finding a pair of shades to complement the latest fashion?

Researchers at the University of Washington in Seattle may have come up with a solution.

The team, headed by Chunye Xu, research assistant professor of mechanical engineering, built a prototype pair of sunglasses that allows the user to quickly and easily dial the desired color and shade of its lenses. The researchers said that the sunglasses would be particularly suited for outdoor activities — such as hiking, skiing and motorcycle riding — where a rapid response to changing light conditions is needed.

TWSun_glasses_combo.jpg

Smart sunglasses are shown in a transparent state (top) and darkened (bottom). The switch to turn on the glasses and change the color of the lens can be seen on the left. Courtesy of Chunye Xu, University of Washington.


The so-called “smart” eyewear relies on an electrochromic polymer in the lens that can modify the level of shading or that can change color when prompted by an electrical current. The glasses are powered by a tiny commercial cell battery with a standard electric capacity of ∼100 coulombs. Turning a button mounted on the frame of the glasses activates the battery and allows the user to control the tint and opacity. The researchers said that the lens can be tuned to a colored state in one second and back to a completely transparent state in two seconds.

The lens of the prototype actually consisted of six layers of material. The researchers placed an anti-UV layer on the top, followed by transparent indium tin oxide glass, an ion storage layer, a transparent gel electrolyte, the electrochromic polymer and then another layer of transparent indium tin oxide glass. A UV-curing epoxy was used as a hermetic barrier to seal the layers.

After more than 100,000 cycles of switching the lens between a transparent and colored state, the researchers found that the device had a less than 6 percent change in transmission on the colored state and almost no change on the transparent state. They also found that the device could stay in a colored or transparent state without any charge for 30 days. A single battery powered thousands of transitions.

They presented their findings in March at the national meeting of the American Chemical Society in Chicago. They are seeking patents for the technology and said that they would be seeking to incorporate their lenses into more stylish sunglasses (the prototype used a bulky pair of lab goggles). The technology could be ready for commercialization within a few years.


GLOSSARY
lens
A transparent optical component consisting of one or more pieces of optical glass with surfaces so curved (usually spherical) that they serve to converge or diverge the transmitted rays from an object, thus forming a real or virtual image of that object.
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