Eye glasses that can be manually switched to "sunglass mode" may be on their way

Eye glasses that can be manual...
The prototype glasses in their tinted and clear states (Photo: American Chemical Society)
The prototype glasses in their tinted and clear states (Photo: American Chemical Society)
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The prototype glasses in their tinted and clear states (Photo: American Chemical Society)
The prototype glasses in their tinted and clear states (Photo: American Chemical Society)

Glasses with transitional lenses are a neat idea in theory, but they have some shortcomings in practice. That's why researchers from the Georgia Institute of Technology are developing an alternative – clear eyeglasses that can be manually tinted into sunglasses, by the user.

The photochromic lenses in transitional glasses contain silver halide molecules that temporarily change shape when exposed to ultraviolet light. This causes the lens to darken, and some of that light to be blocked.

One of the problems with them, however, is that the transition from clear to tinted can often take up to a few minutes. When you're performing activities such as driving or even flying a plane, that's simply not fast enough. Additionally, they won't tint if you're in a shaded place – such as the inside of a car – looking out onto a brightly-sunlit area.

By contrast, users of the Georgia Tech glasses can tint and un-tint them whenever and wherever they want, just by flipping a power switch.

The lenses contain electrochromic polymers, which respond to electrical current instead of ultraviolet light. In the prototype glasses, a mix of cyan, yellow, orange and blue polymers was used to create a brown tint, that blocks up to 70 percent of incoming light within a few seconds. By changing the ratios of the polymer colors, however, other colors of tints could also be achieved.

According to the research team, which was led by Anna Österholm, the inkjet printing/blade-coating technique used to create the lenses could easily be scaled up for commercial production. In fact, New Jersey-based startup Ashwin-Ushas is currently developing electrochromic sunglasses of its own, that use a photodetector to automatically adjust the level of tinting.

A paper on the Georgia Tech research was recently published in the journal ACS Applied Materials & Interfaces.

Source: American Chemical Society

What about blocking UV? Without that ability having darkened lenses is actually a safety issue. Hope that is part of the package.
That said, I want this very much. Can't wear contacts and I keep losing my prescription sunglasses.
Organic polymers usually degrade over the long term, whereas silver halide, being inorganic, is essentially permanent. 70% light blockage is also a little too high for sunglasses. My Serengeti photochromic sunglasses block more than that at their lightest and up to 91% at full darkness. Non-photochromic glacier glasses go to 95% and over.
Gregg Eshelman
The photogrey or photobrown lenses have the tinting material as part of the lens and they change based on the level of visible light. Put them in a dark place long enough then take them out and the ground edges of the lenses will appear yellow, until they're in light long enough to darken.
Transitions(TM) use a UV sensitive coating and are faster reacting but are pretty much useless for driving because automotive window glass blocks too much UV light.
Having glasses that switch from normal to sunglasses would be awesome. That way you wouldn't have to change glasses every time the sun came out. This would be something my wife would love. She is always complaining that she has to take her glasses and sun glasses with her everywhere she goes. Thanks for the great post.