Contrast structures phase plane cell

The application of an electric field above the threshold value results in a reorientation of the nematic liquid crystal mixture, if the nematic phase is of negative dielectric anisotropy. The optically active dopant then applies a torque to the nematic phase and causes a helical structure to be formed in the plane of the display. The guest dye molecules are also reoriented and, therefore, the display appears coloured in the activated pixels. Thus, a positive contrast display is produced of coloured information against a white background. The threshold voltage is dependent upon the elastic constants, the magnitude of the dielectric anisotropy, and the ratio of the cell gap to the chiral nematic pitch ... 

A lyotropic L.C. consists of two or more components that exhibit L.C. properties in certain concentration ranges. In the lyotropic phases, solvent molecules fill the space around the compounds to provide fluidity to the system. In contrast to thermotropic L.C.s, these lyotropics have another degree of freedom, i.e., the concentration, which enables them to induce a variety of different phases. Since lyotropic L.C.s rely on a subtle balance of intermolecular interactions, it is often more difficult to analyse their structures and properties than those of thermotropic L.C.s. Lyotropic L.C. nanostructures are abundant in living systems. Accordingly, lyotropic L.C.s attract particular attention in the field of biomimetic chemistry. In particular, biological membranes and cell membranes are a form of L.C. Their constituent rod-like molecules e.g., phospholipids) are organized perpendicularly to the membrane surface, yet the membrane is fluid and elastic. The constituent molecules can flow in-plane quite easily, but tend not to leave the membrane, and can flip from one side of the membrane to the other with some difficulty. These... 

---