Question: how many liquid crystals types are there

Jess Wade answered on 15 Jun 2015:

This is actually a pretty tricky question, so I’m going to try and answer it in two ways.

I think you might be thinking about liquid crystal television screens. When I was little our television sets used to be huge and were made of cathode ray tubes. These basically worked by firing a little electron across the tube, the electron would hit the screen and interact to make the picture we saw on the screen. But everyone wanted thiner TVs that they could put on the wall, so we made up LCD (liquid crystal display) screens. Here we have a big grid of little pixels ofthree different colours (red, blue and green). We choose which picture we send the current to and make it light up or turn off. It means we can make much thinner screens.

As for liquid crystals that aren’t TV screens, these are actually states of matter. Just like we think about solids, liquids and gases there are some complicated bits inbetween. Inbetween a solid where everything is arranged super nicely (an ‘ordered’ solid) and a messy liquid where everything is wobbling around, there is the ‘liquid crystal state’. Even inside this new state of matter there are lots of different ways the material can be depending on how ordered or disordered it is. They all have funny names like ‘nematic’ and ‘smectic’, which describe in which direction the molecules are arranged. Smectic comes from the greek work for soap, and is called that because the thick soapy substance at the bottom of your soap dish is actually a liquid crystal!