Visualization of the topological defects in liquid crystal cells

PhD student Pavlo Golub (Ukraine)

Video was recorded during the 7th International research and practice Conference "Nanotechnolgy and Nanomaterials" (NANO-2019)

We report the series of the experiments which main aim was the visualization of a topological defect i.e. making it visible with naked eye. The several methods of the visualization are proposed and discussed. We observed that small spheres with size about 1 µm and same sized diamonds and cylinders are well visible in the liquid crystal (LC) cell, but they produce strong distortion of the order parameter around them and, as result, distortion of the disclination itself.

Other objects that were used to visualize the topological defect were bubbles and it was first observed that quite big bubble (up to 0.5 mm) could be moved by the disclination without strong distortion of the disclination and disordering. However the bubbles are easily aggregated to one big bubble which is hard to move by disclination in a cell.

To visualize the motion of the defect the jump of the selective reflectance wavelength on the defect could be used. It is well visible in thin cell and causes no distortion in LC order. It can be used for precise measurements of chirality variations and other measurements based on external influence.