A bright field microscope shows how nanowires distort an elastomer when voltage is applied.
Electrochemical smart windows are pricey because they're painstakingly coated using vacuum deposition (Samsung's crazy OLED windows are in another league altogether). Harvard's tunable window, on the other hand, is made by sandwiching glass or plastic between soft elastomers that are sprayed with silver nanowires. The nanowires are too small to diffuse light, but squeeze together when you apply current, deforming the elastomer. The randomness of the coating allows light to pass but heavily distorts it, giving you similar privacy to frosted glass or sheer curtains. By varying the voltage, you can have different levels of privacy.
The voltages required are still too high, so the team is trying to make the elastomers thinner to reduce the draw. Once the materials are perfected, however, nanowires could be sprayed directly onto special windows, making the tech feasible for large projects. "Because this is a physical phenomenon rather than based on a chemical reaction, it is a simpler and potentially cheaper way to achieve commercial tunable windows," says Harvard's David Clarke.