Condensed state physics in biology: Liquid crystal - semiconductor system

Abstract

The possibility of application of condensed state physics methods for the study of biological objects is considered. The object of use is a cell with a liquid crystal as a model of a biological system - a living cell. The system of liquid crystal - semiconductor was experimentally investigated by methods of modulation spectroscopy. By determining the value of electric reflection, it is possible to judge about the state of surface polarization of liquid crystal. Exposure to an electric field changes the energy of the semiconductor’s zone structure, which leads to changes in the optical properties of both crystals. To investigate the optical modulation changes in our case, we used the method with the use of electrolyte KOH, which allowed us to measure the modulation of the spatial charge. The study of thin layers (up to 120 μm) of various nematic liquid crystals has shown that at values of electric fields comparable to the Fredericks transition threshold, the orientation angle of liquid crystal molecules changes due to the interaction of surface polarization with the external field, and an odd electro-optic effect is observed. If the value of the electric field is much larger than the threshold of the Fredericks transition, the electric moment, which depends nonlinearly on the field, predominates and leads to an even electro-optic effect. The results of the study are proposed to be used for the development of new drugs and materials with specified parameters for medicine.