From glasses to sunglasses in the blink of an eye

Although ‘tinted lenses’ have been available for some time, a new technology uses electrochromic polymer blends to allow users to block out daylight at the flick of a switch.

Existing technologies commonly used in glasses are not always effective. Most transitional lenses now on the market don't meet many users' needs. When wearers are driving or wearing a baseball cap, for example, the lenses stay clear rather than switching to a darker shade even in broad daylight. Also, the majority of available versions don't block out the harshest light, such as bright light reflected off snow. And the change from colored to clear can take several minutes, which has safety implications for certain users including airline pilots.

A new study by Anna Österholm in John Reynolds' group at the Georgia Institute of Technology uses electrochromic polymer blends to provide faster lens property changes. Funding for the study comes from chemicals giant BASF.

The researchers designed a new kind of lens that can switch within seconds from clear to darkly shaded and back again in response to a small electrical charge that a wearer could control. They can also fine-tune the color of the lenses to match the full range of hues used in commercial sunglasses. To make the lenses, they say they used a method that could be easily scaled up for manufacturing.