Any material present around us exists in one of the three well-known phases – solid, liquid or gas. Apart from them, there are some other substances that tend to have the nature of both solid and liquid. Such substances are called liquid crystals.
In solids, the molecules remain closely packed in fixed position and orientation. In liquids, they are packed closely but still can move around. That is why liquids don’t have a specific shape but they take the shape of their container. Gases have no fixed shape too but are little resistance to compression. That is why they try to expand to fill its container instead of settling at the bottom.
Liquid crystals as the name suggests are not solid crystals and not liquid altogether. They are substances that tend to maintain their orientation like solids but are free to move like liquids. It was in the year 1888 an Austrian botanist Friedrich Reinitzer discovered the existence liquid crystals. Cholesteryl Benzoate was the first liquid crystal to be discovered. There are three phases in which the liquid crystals exist – nematic, isotropic or smectic phase depending on how their rod shaped molecules are oriented.
The most common applications of liquid crystals are liquid crystal thermometers and liquid crystal displays (LCDs) like those in watches, microwave timers, calculators, TVs, computer monitors etc.
In order to convert solid into liquid, it needs lot of heat energy. As liquid crystals are quite close to liquid phase, it would only take less amount of heat energy to turn it to liquid. Their sensitivity to heat is what makes them useful in making thermometers.
LCD TVs, LCD monitors have become very common. The display consists of two glass plates with liquid crystals in between them. Liquid crystals in nematic phase with their sensitivity to electric current make the ‘liquid crystal display’ possible. They are twisted in their natural form and when an electric charge is applied, they untwist. When they straighten out, they change the angle of the light passing through them. The greatest advantage of a LCD display is that use of LCDs brings down the size of the device. For examples, LCD TVs don’t have the bulky picture tube like the conventional ones. Also LCDs consume much less power.