Eyeglasses that darken into sunglasses have been available for many years, but many people have some issues with them. These transitional lenses darken when they are exposed to sunlight, but the process can take several minutes. Often, the lenses will stay clear and not darken if they are being worn in a car or while wearing a hat with a wide brim. They also may not get dark enough to block out very harsh light. The process is a passive one and the lenses cannot change on demand.
Now, chemists are creating eyeglass lenses that change from clear to darkly shaded and back again at the flip of a switch. The lenses change color in response to a small electrical charge that the eyeglass wearer can control. The color and darkness of the lenses can also be modified.
Researchers at the Georgia Institute of Technology in Atlanta, Clayton State University in Morrow, GA, and at the BASF Corporation have created a strategy to create a wide variety of colors in lenses by use of electrochromic polymers. These polymers reversibly change color when a burst of electric charge is applied. The researchers created several shades of brown electrochromic polymers by using various combinations of cyan, yellow, orange, and periwinkle blue. When an electric charge is added, the lenses darken.
The eyeglasses they created using the electrochromic polymers provided a rapid high-contrast change from colorless to dark or back again, a process that takes only seconds. They also showed that the method can be used in large scale manufacturing.
Drivers, airline pilots, and police are among the people who could use eyeglasses that change rapidly to sunglasses and back again.
The research was published in the journal ACS Applied Materials & Interfaces, a publication of the American Chemical Society.
