Because it’s so effective at reflecting UV radiation, and can be pounded thin enough to see through, gold has been used for many types of specially-designed windows. However, researchers David Clarke and Samuel Shian at Harvard University have developed a new type of window that uses silver nanowires for adjustable transparency.
Windows with controllable transparency are not a new technology, but they work completely different from what Harvard has developed. Today’s adjustable windows use glass coated with organic photochromic molecules. When exposed to UV rays, a chemical process causes the molecules to change shape and absorb much of the visible light (i.e. they darken). While effective at blocking light, the manufacturing process for these windows is difficult and expensive.
Clarke and Shian’s technology uses normal glass sandwiched between two clear elastomer layers that have been sprayed with silver nanowires. The nanowires are so small, that they do not perceptibly affect the transmission of light on their own. But when an electric current is applied, the nanowires on either side of the glass are drawn towards one another – deforming the soft elastomer from smooth to rough, which scatters the light and instantly decreases the window’s transparency. By adjusting the current, you can customize how much light passes through the glass.
Because the manufacturing process for silver nanowire windows would be cheaper and easier than their chemical counterparts, the researchers are hopeful that their technology could reach a commercial scale. Already, Harvard’s Office of Technology Development has filed a patent application and is reportedly in-talks with potential licensees in the glass manufacturing industry.