Researchers at the University of Washington (Seattle, WA) have designed prototype sunglasses that darken instantaneously, using electrochromic materials that change transparency depending on the electric currents running through them. The wearer spins a tiny dial on the arm of the glasses to change lens color or shade.
Sandwiching a gel between two layers of electrochromic material created the lenses. Applying a small voltage moves charged particles from one layer to another, changing the transparency. A single watch battery is able to power thousands of transitions. Once the glasses are a certain tint, they will stay that way without power for about 30 days. Organic molecules allowed the researchers to create colored lenses.
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