Surface-induced orientation of liquid crystal phases

Liquid crystal (LC) phases have been used in various self-assembly technologies owing to their stimuli-responsive characteristics. Especially, orientation-controlled LC structures on and in surfaces are extensively studied in physics, chemistry, and materials science because they can be used in patterning applications beyond the conventional LC display. The key idea in recent development is to control the surface anchoring condition between the substrate and LC materials. Specifically, defects in the LC phases have been introduced as an effective lithographic tool for fabricating distinguished patterns. In this review, the bulk and surface-induced structures of LC materials are overviewed to show the relationship between the surface characteristics of the substrates and the elastic properties of LC materials. The two main themes are (1) orientation control, which can be achieved by micro- and nano-confinement using solid and fluid substrates, and (2) the application of LC materials as optoelectronics and sensors. Finally, the review discusses the defect structures of LC materials fabricated on flexible substrates and their possible applications.