Researchers have been trying to coat contact lenses with light sensitive dyes to have them turn dark during bright lighting conditions. Glasses with this property have existed for decades, but the same coating methods are not applicable to contacts.
Technology Review reports on work by the Institute for Bioengineering and Nanotechnology (IBN) in Singapore to use the entire volume of the lens to contain the dye:
Conventional transition sunglasses are coated with millions of molecules of photochromic dyes, which are transparent when out of the sun. These molecules change shape when UV light hits, enabling them to absorb UV light and triggering the darkening of the lens. When UV light disappears, the molecules change back to their original shape and transparent appearance.
Few previous attempts have been made to design transition contact lenses, largely because it’s difficult to apply dye coatings uniformly to the delicate, soft surface of a contact lens. Ying and her colleagues got around this by developing a contact lens that embeds dyes uniformly throughout the material. This approach allowed them to pack more dye molecules into the material, Ying says, giving the contact lens greater sensitivity to light and thus a faster response.
Researchers created the spongy nanostructure material by mixing specific combinations of water, an oil solution with monomers commonly used in contact lenses, and a novel surfactant– a compound that encourages mixing between water and oil solutions. The resulting material is studded with tiny pores and tunnels, which can be loaded with agents such as UV-sensitive dyes.
Read on at Technology Review…