New Tunable Windows Turn Opaque with Switch--Tungsten Trioxide

Imagine a window with no need for cumbersome blinds, but just with a flick of a switch, the glass simply turns opaque. Tungsten trioxide is the material that can be used for preparing tunable windows, the thin coating made by it vacuum deposited on glass. When electricity is applied, it triggers an electro-chemical reaction that turns the material opaque.



The window is made from a stiff sheet of thin plastic or glass, which is inserted between two layers of a transparent rubbery material called an elastomer. The researchers then cover both sides with a network of silver nano-wires. The nano-wires, each a few microns long and 90 nanometers across, are scattered randomly, similar to a game of pick-up sticks. The tiny nano-wires don't scatter light and sparsely cover the surface, leaving the window transparent. But when the electric voltage, it changes. The change in transparency happens quickly, in less than a second the material’s color has been changed without your observing.

This uneven surface scatters light just like how waves on a pool's surface prevent you from seeing into the water. But one of the biggest advantages of using tiny nano-wires is a potentially cheaper and simpler manufacturing process. On the other hand, expensive high-vacuum technology to produce is required.

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