The current smart windows based on polymer dispersed liquid-crystal (PDLC) and electrochromes are still not cheap enough for household applications. A flat glass is clear while a frosted glass with microrough surface appears translucent by light scattering. Motivated by this optical surface scatterer, we developed an active smart window based on a soft capacitor with voltage-tunable surface roughness. This active smart window switches between clear and frosted (from 80 to 1% in-line transmittance) and demonstrates tunable diffusion, better than conventional smart window based on PDLC.
Technology Features, Specifications and Advantages
This TiO2-based surfaces of high transparency attain a much wider range of transparency tuning between 81% to 1.85% transmittance at the least actuation (of not more than 5% strain). This excellent tunability even exceeds the reported tuning range (e.g. 6% and 62% in-line transmittance) of a commercial PDLC window. This all-solid state device consumes low power of less than 1W/m2 to switch to be clear.
We tested out this window device to diffuse lighting and provide privacy. When being inactive, this window device appears translucent to diffuse the backlighting, and to hide the colour blocks behind it. When being activated, the device turns transparent to show the backlight source glaring and the colour blocks behind it. Such tunable light diffusion can vary the shadows from blurred to defined. This tunable optical diffuser could also be handy for cinematography lighting, removing the need for manual changing of lighting diffusion gels/filters. In addition, it will be useful as a tunable sun visor against sun glare.
Without the use of exotic materials other than sun-block material and adhesive, the cost to make this device is low and is less than 10% of the price of PDLC. When mass-produced, this device can be sold for $10/m2. This low-cost device technology will make smart window common for home adoption, in addition to office and shop. We can license the know-how and patent to glass makers to promote common adoption of this technology.