There are different kinds of smart windows in the market. However, most of them take more than 20 minutes to dim, and become less opaque over a period of time. Engineers from Stanford University in the United States have developed smart windows that can be switched between transparent and opaque with a touch of button within a minute, and do not degrade easily over time.

The durability of the Stanford prototypes has been demonstrated in more than 5,000 times of switching the windows on and off, and no degradation in the transmission of light is observed. The prototypes are made of conductive glass outlined with metal ions that spread out over the surface, blocking light, in response to electric current. When transparent, the windows are clear and 80% of ambient light is allowed to pass through, and when dark, transmission of light decreases to under 5%. Using the electrochromic technology, tinting of the windows used in these prototypes can be controlled electronically, and users have control over the level of tint they want.

The researchers have filed a patent for this new technology and have entered into discussions with potential manufacturers. However, more researches are needed to make the surface area of the windows large enough for commercial applications.