Joint Seminar by SKL, ECE Dept and SID - Flexoelectric in Liquid Crystals and Its Applications

Nematic liquid crystals of specially shaped molecules, such as “banana” and “pear” shaped, in special confinements or configurations exhibit spontaneous electric polarization, a phenomenon known as flexoelectric effect. They can be reoriented by externally applied electric fields through two interactions. One is the regular dielectric interaction, which is not sensitive to the polarity of the applied voltage. The other one is felxoelectric interaction, which is sensitive to the polarity of the applied voltage. The dielectric and flexoelectric interactions have different dependences on the frequency of the applied voltage. Flexoelectric interaction is dominant in low frequency region (~10 Hz) and can align the liquid crystal in one direction, while dielectric interaction is dominant in high frequency region (~1000 Hz) and can align the liquid crystal in another direction. Therefore the liquid crystal can be switched to different states by varying the frequency of the applied voltage. The flexoelectric and dielectric effects can be made use to develop many devices, which are impossible under only dielectric interaction. In my talk, I will discuss the mechanism of flexoelectric effect. I will also discuss its applications, such as reconfigurable optical grating, light waveguide liquid crystal display, dual mode smart switchable window and bistable polymer stabilized cholesteric texture smart window.