Smart Glass varies its light transmission properties under light, thermal, and electrical influences. Smart Glass has two broad categories: passive and active. The passive subcategory, includes thermochromic and photochromic. The active subcategory, includes electrochromic (EC), suspended particle devices (SPD), and polymer dispersed liquid crystal(PDLC).
Passive smart glass technologies are those that use natural, nonelectrical stimuli, such as heat and light, to transition from dark to light and vis versa.
Thermochromic glass, uses heat from direct sunlight to tint windows on an as-needed basic. As the amount of direct and intense of sunlight increases on the glass, the darker it becomes.
Photochromic glass will change level of transparency in response to the light intensity.
Active smart glass technologies are those that respond to an electrical stimulus, which gives the control to the user, by providing an on-demand results.
Electrochomic (EC) can switch its color by applying external DC voltage or current, turning the glass from clear to dark. Typical use includes solar control for exterior glass. Electrochomic darkest state, the visible light transmission can be less that three percent, with limited privacy as it can still be seen through.
Suspended particle devices (SPD) is small light-absorbing microscopic particles, that response to an external AC power source in a matter of seconds transitioning from clear to dark. When voltage is applied, the suspended particles align, which allows light to pass. This technology generally used for light-control applications – most commonly auto glass, skylights, sunroofs, portholes, aircraft windows, and marine windows. It provides weak to moderate privacy.
Polymer dispersed liquid crystal (PDLC) is an innovative technology that switches from opaque to clear in milliseconds using AC current, regardless of the size of glass. It has light-scattering power when electric field is applied, and can be used for a range of exterior and interior applications. Products using this technology are available in a self-adhesive switchable film that can retrofit to existing surfaces and well as a laminated switchable glass. In its opaque state, it gives the user complete privacy, since you can’t see thru it.