What is inside your flat screen TV? If you have looked at a calculator or a mobile phone display, used a laptop or a flat screen TV you’ve made use of liquid crystals in the form of liquid crystal displays (LCDs). However, liquid crystals have a whole range of uses, from thermometers to bullet proof vests! Liquid crystals are also found in living cell membranes and even the slime in your soap dish is made of liquid crystals.
Why is this important?
Look around you. How many things do you think contain liquid crystals?
You may be surprised by the answer. Liquid crystals are a multi-billion dollar industry and these fascinating materials are used as displays in a range of products including flat screen TVs, mobile phones, and laptops.
The special properties of liquid crystals - having their molecules arranged in order, but still being able to flow like a liquid - means that they have specific optical effects, which are perfect for showing images in electronic devices.
In liquid crystal displays, an electric field changes the orientation of the liquid crystal molecules. This affects the polarisation of the light waves that are transmitted by the liquid crystal. Red, green and blue colour filters can be placed on each pixel of the display, and colour images are produced, like in LCD TVs or laptops, in contrast to the simple black and white displays of pocket calculators. The image on the right shows magnified individual pixels of an LCD TV screen.
Liquid crystals and life
Liquid crystals are also fundamentally important to life. DNA and cell membranes have liquid crystal phases. Our brains are around 70% liquid crystal, and liquid crystals are also found in muscles, the amazing iridescent colours of some insects, and also slug slime!
Where else can you see liquid crystals?
In your home, liquid crystals are not only in electronic devices, they are also in your washing up bowl! Liquid crystals are in soap and detergent. The slimey stuff that collects in the bottom of soap dishes is soap in a liquid crystal phase.
Liquid crystals can form different types of modern materials. There is a polymer called Kevlar® which is made from the liquid crystalline state, giving a strong fibre - as strong as steel at only 1/5th of the weight! This type of polymer is used to create bulletproof vests, firemen's protective gear, sails on boats and the ropes used in climbing.
Special sheets made from liquid crystals are also used in industry to look for hot spots in machinery (which might be a signal that an electrical device has failed), to map heat flow and to measure stress distribution patterns. This is because the liquid crystals will change colour with temperature, and the temperature depends on material failure or infections or tumours. The picture below shows two hotspots showing up in liquid crystal.