Research on liquid crystals (LC) started in mid 18th century. In 1850 W. Heintz discovered that stearin (a biochemical compound) changed its optical properties when its temperature is raised. In 1888 Friedrich Reinitzer discovered the basic principle behind liquid crystals. Lehmann and others stated liquid crystals as a new phase of matter. In 1991, Pierre-Gilles de Gennes received the Nobel Prize in physics for designing simple systems to measure complex phenomenon, especially with respect to Liquid crystals.
Liquid crystals are present in biological systems and are part of important biological functions and units like DNA, cell membranes and polypeptides. Collagens and Dragline Silks (spider web) are some biological compounds that behave like liquid crystals. Lipids (one of the most common biological compounds) show liquid crystal properties near their melting temperature. Biological compounds form a separate class of materials: liquid crystal elastomers(LCEs).
There are generally three liquid crystal phases: metallotropic, lyotropic and thermotropic. The metallotropic phase has both the organic and the inorganic crystals. Transition liquid crystal material in the metallotropic phase depends on the temperature and the concentration and ratio of inorganic: organic crystals. Thermotropic and lyotropic phases consist of only organic crystals. In the case of lyotropic phase, transition depends on changes in the temperature and the concentration. In the case of thermotropic phase, transition depends only on changes in the temperature.
The properties of liquid crystals are dependent on the orientation of the molecules of the material. Properties of liquid crystals are dependent on the direction in which the force is applied. Due to this, when a liquid crystal compound is flown through two close plates, dendritic patterns are formed. Properties like surface tension, ratio of equilibrium structures and thermal conductivity also show this anisotropic behavior.
Scientists have long tried to cover major aspects of phase transition in liquid crystals. Many factors play role in the complex interactions of the LC material. High material density, hardcore repulsions and multiple body correlations interact together to couple the orientation of the molecules with the force (impact). The direction of the orientation is defined by a vector called director.
Liquid crystals find its application in liquid crystal displays, thermometers and semiconductor industry .They are also used as memory units in space shuttle equipments. They consume less electricity and hence provide better alternative to LCDs. New researches are targeted towards devising ultra-low energy utilizing LCD panels. Liquid crystals also find application in biotechnology (biosensors).
The discovery of liquid crystals has revolutionized the digital world. It has enhanced TV viewing experience for the masses. At the same time, it has made possible for mobiles to have a vibrant display. It has also lead to development of a new generation of laptops and tablets. LCs can be used in various applications. Its future lies in its application in energy-efficient displays and systems.