Switch Glass

Switch glass, turning curtains obsolete?

Windows. Your home wouldn’t be the same without them. However, they are but a mistress in our marriage with privacy. We literally hide them behind a curtain, if we want our beloved privacy. Now, wouldn’t it be everyone’s dream to find someone, or in our case, something that offers the best of both worlds?

Around 100 B.C. the Romans figured out how to increase the transparency of glass and started using it for tiny windows. However, it wasn’t until the 20th century that we managed to create considerable flat surfaces. From that moment on, science took control over its developed… Double-glazed windows, sound and bulletproof glass and now even controllable glass?

Switch glass is basically a transparent material that turns opaque and vice versa with just a push of the button. Honestly one of the more classy ways when it comes to offering privacy! The switching process is caused by an electrical current that aligns the nematic liquid crystals with the polymers they are absorbed in. Let me break it down for you.

Liquid crystals (LCs) are formed by long and narrow molecules, also known as the calamitic molecules. They are absorbed by a transparent polymer with the same refraction properties as regular glass What about that nematic state? If you thought materials could only exist in three states, this glass is the example to prove you wrong. In this glass LCs are in this nematic state, a difficult way of saying that they show properties of both the solid and liquid phase. The molecules can move around freely like a fluid, but self-align and create a directional order, similar to the structure of solid materials. This is where things get interesting. In this intermediate state, LCs are easily aligned by an external magnetic or electric field, which makes it controllable. And there’s more, when aligned, these crystals have the exact same optical properties as regular glass.

With all attributes and properties combined, it’s possible to change the transparency of this ensemble. Without electrical current, the LC droplets are randomly displaced and, because the refractive indices of the materials don’t match, light scatters and the glass appears opaque. However, when a current is applied, the LC’s molecules do align and its refractive index matches that of the polymer. Incoming light goes right through the device and the glass becomes transparent.

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Reference:

M. Reyniers, Scheikunde: Capita Selecta