April 6, 2007 — Sunglass lenses that transform automatically from clear to dark are old hat. Now new lenses with chameleon command can change not only from clear to dark but also to shades of yellow, green and purple.
The switch between shades occurs much faster than conventional tinted lenses and could offer an endless range of options for enhancing visual contrast, improving depth perception, brightening low-light conditions and offering aesthetic appeal.
"These lenses are more controllable, more active, more intelligent and dramatically improve lens functions," said Chunye Xu, principal investigator and research assistant professor at the University of Washington. Xu collaborated on the project with Minoru Taya, professor of mechanical engineering, and doctoral student Chao Ma.
The lens material is made from a plastic, or polymer, that changes transparency when zapped with an electrical current. The whole lens includes a clear, protective layer, a base of titantium oxide and a gel-like solution in between the layers that helps transport charged particles. A watch battery delivers the charge. On the prototype glasses, the wearer spins a tiny dial on the arm to change color or shade.
Unlike other so-called electrochromic materials, this polymer is made from cheaper organic chemicals — as opposed to more expensive inorganic chemicals. And it's able to change from a clear to colored state in one to two seconds, while maintaining the state without a constant injection of power. This could ultimately make the lenses more economical to manufacture and power, said Taya.
"This work is very innovative," said Guoqiang Li, associate research professor of optical sciences at the University of Arizona in Tucson. "The most important thing that is different from previous work is it has a memory function, which means that when the device is tuned to a transmission state, it can stay there for a relatively long time without power."
To date, the team has successfully developed a blue lens and is currently working toward incorporating red and green. Having all three colors will allow them to produce any color of the spectrum as well as shades of black.
Xu's group is also working on smart windshields for aero vehicles and ground cars as well as smart windows for energy-efficient homes and offices.
The team has filed for a number of patents is talking with local companies about commercialization. But it will be a few years before we'll be dialing up the color on our sunglasses.
