What is Smart Glass?

"Electric glass" may sound like the name of a '70s rock band, but it's becoming a 21st-century reality. The operative term is "smart glass," and its applications are as varied as the uses of glass itself. Through this technology, glass can turn from transparent to opaque, control the passage of heat and light and convert itself from two-way to one-way, all at the behest of the user.

In basic terms, smart glass operates by using electric voltage to affect the alignment of microscopic particles within the glass. In the case of electrochromic devices, these particles align or disperse to change between translucence and transparency as soon as an initial electrical impulse is introduced. After that, the conversion takes place on its own with no additional electricity needed. Another electrical application will then reverse the process.

The change takes anywhere from seconds to several minutes to take place, beginning at the edges of the glass and moving inward. In its "resting" state without electric current, some smart glass presents an opaque appearance. Other types are reflective.

Applications for smart glass include building windows, doors and skylights; automobile, boat and aircraft windows; appliance windows, computer screens and cell phone screens. Its use in home and residential windows can all but eliminate the need for blinds or shades, and it fits in with the "green movement" by helping with interior heating and cooling.

Some aspects of the technology feel comfortably familiar. The knob or sliding control used in some electrical "smart windows" is much like that long used to lower or increase the intensity of a light. Meanwhile, a related "passive" smart glass technology works in much the same way as sunglasses that darken in response to a light stimulus.

As with many innovative products, however, smart glass is pricey on the front end -- as much as 400 percent costlier than standard glass. This has proved a barrier to companies raising high-rise structures with hundreds of windows. It can be argued, however, that the energy-saving qualities of smart glass can pay for that differential over its lifetime. Research is also being done into retrofitting standard windows to incorporate smart glass technology.