Alignment control of thermotropic liquid crystals by topography and chemical functionality of a surface: A review

The essential difference between liquid crystals (LCs) and conventional fluids is their ordered molecular orientations. Since the discovery of LCs, how to control their molecular orientation has always been a matter of concern, as this is the basis for most applications of LCs. The molecular orientation of LCs is affected by many factors, and a lot of methods have been developed to control the alignment of LC molecules. The surface induced alignment is undoubtedly the mostly widely and most important one, since in almost all applications of LCs, the contact between LC and other surfaces is inevitable. In this paper, we briefly review the surface topography and chemical functionality induced alignment of LC molecules. Firstly, the common characterization techniques for LC alignment are briefly introduced. Then the surface topography, chemical functionality and their synergistic effect on alignment are discussed, hoping to provide a reference and inspiration for researchers in various application and research fields of LCs.