ABSTRACT
This chapter describes the peculiarities of nematic (N) phases observed in bent-shaped molecular systems. Elastic constants are one of the most important material constants in N liquid crystals (NLCs), because they are directly correlated to the electro-optic performance in display devices. The discovery of flexoelectric effect in NLCs dates back to 1969. Due to its remote similarity to the piezoelectric effect in crystals, flexoelectric effect has been thought to have potential applications for electromechanical devices such as touch sensors, strain gauges, and actuators. On a microscopic level, the flexoelectric effect can be pictured as a coupling between the curvature distortions of the director field with the shape polarity of the consisting molecules. It is particularly well seen for the cone-shaped and the bent-shaped mesogenic forms. An overview of research in the field of biaxial N liquid crystalline materials was given by Tschierske and Photinos, summarizes the theoretical concepts, material design, and identification methods.
