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I read about a new smart wall (glass) from NanaWall.
nanawall.com/products/whiteout

I was wondering how it worked. So far I only learned something about nematic liquid crystal displays (LCD). With the following cell configurations Fréedericksz cell, VA cell, twisted nematic LC cell (similar to the Fréedericksz cell).

I read a little in a book [1] about polymer dispersed LCDs (PDLCDs).
These displays can address states between a scatter mode, where the display looks like a opal glass panel, and a transparent mode. With a contrast ratio of approx. 40:1, compared to a newspaper with a contrast approx. 8:1.

That sounds very similar.

Some more information about PDLCDs:
The nematic liquid crystals are arranged as droplets in a polymer binder between two glass plates with electrodes.
These droplets have a random orientation and so the refractive index is random. This causes the light to be scattered at a wide angle to the observer (scattering mode).
By apply an electric field the molecules orient themselves parallel to the field. With the result that the refractive index is almost the same. This means that the light can not scatter through the display (transparent mode).

This type of display don’t require a polariser.
I think that’s a big advantage of this technology. This way don’t lose 50-60% of the light beam at the polariser. This enables us to achieve a high transmission rate.
In my opinion, one disadvantage is that we need an applied electrical field for the transparent mode. Because in this case I don’t want an opaque window at a power blackout.

This was just one possible technology. Wikipedia [2] lists these technologies: electrochromic, photochromic, thermochromic, suspended-particle and micro-blind and polymer-dispersed liquid-crystal devices.

Maybe you have another idea.

Now it's time. Good night.

[1] Liquid Cristal Displays, Addressing Schemes and electro-optical effects, Ernst Lueder

[2] en.m.wikipedia.org/wiki/Smart_

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