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Published on July 17th, 2015 | By: Stephanie Liverani


Cool shades—sunglasses that turn from dark to clear with the push of a button

Published on July 17th, 2015 | By: Stephanie Liverani

[Image above] Credit: Thomas Beck; Flickr CC BY 2.0



I know a few bespectacled folks who, for simplification, rely on photochromic lenses. You know, the glasses that release you from the burden of having to tote around indoor specs for reading and a separate pair of prescription sunglasses so you can brave the harsh mid-afternoon sunlight?


It makes perfect sense. Photochromic lenses provide a convenient two-in-one solution for those who need prescription lenses, indoors and out. These special lenses are designed to use the sun’s UV rays to turn the glass from clear to tinted—but the change isn’t instantaneous.


Because current photochromic lens technology reacts specifically to UV light, this leads to some challenges. For example, most modern car windshields use UV-filtering glass that impedes the lenses from darkening completely. And wearing photochromic lenses at high altitudes where there’s too much ambient UV light causes the lenses to remain darker for longer, even indoors.


So for photochromic lens wearers who are tired of trying to read the lunch menu through still-tinted glasses, or need relief from squinting into the sun’s glare bouncing off the car in front during the morning commute to the office, a one-button solution is in the works.


A group of researchers at the Georgia Institute of Technology in Atlanta have developed a polymer coating for glass that can change the lens color instantly with a small, user-controlled electrical current. They published their work in the American Chemical Society’s Applied Materials & Interfaces.


John Reynolds, professor of chemistry and biochemistry, materials science and engineering at Georgia Tech and his team—research scientists Anna Österholm and Eric Shen, and graduate student Ray Bulloch—demonstrate the process in a recent video from ACS.

Credit: American Chemical Society; YouTube


“Our technology is fully user controlled. So the lenses can change their color, going from dark to clear, just by pushing a button,” says Österholm in the video.


The polymer coating uses electrochromic polymers (ECPs)—or polymers that “change color when you apply a potential or a current,” Shen clarifies.


The material also allows for a wide spectrum of color options for the coating.


“You can target and tune the color properties of these mixtures just based on the weight compositions of the mixtures you produce,” says Bulloch. It’s as simple as blue polymer + yellow polymer = green polymer, ACS illustrates in the video.


And this material can be used on more than just lenses. Reynolds says the polymer technology can be printed or sprayed onto large-format applications like billboards, too.


But when asked about the time-to-market for sunglasses on demand, Reynolds can’t promise a definitive timeline for when this technology will reach consumers.


“It’s at that point right now where prototypes can be made and tested. To say when it would come on the market, you’d have to talk to someone in marketing—not the chemist here,” Reynolds says in the video.


And while we don’t know when we’ll actually see this new technology out of the lab and on to the shelves, Shen says it’s just on the horizon.


“What excites me most is just how close we are to seeing this material actually moving out of the lab and becoming a reality to everyone else as well,” says Shen.


The paper, published in ACS Applied Materials & Interfaces, is “Four Shades of Brown: Tuning of Electrochromic Polymer Blends Toward High-Contrast Eyewear” (DOI: 10.1021/am507063d).

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