Sunglasses change colour at the wearer's command

Consumers could soon be able to buy sunglasses that change colour on command in shades of yellow, green or purple.

Researchers at the University of Washington claim that unlike current photochromic sunglasses, which darken in sunlight, the new lenses change electrically, allowing wearers to alter the shade at will.

The university has been developing electrochromic materials for so-called 'smart windows' that could soon be used in energy-efficient homes and offices. Most smart windows use liquid-crystal technology or inorganic oxides but the new glasses are based on a new type of smart window using organic, rather than inorganic, oxides.