Surface-Mediated Alignment of Long Pitch Chiral Nematic Liquid Crystal Structures

Chiral nematic liquid crystals are stimuli-responsive soft materials that can self-organize into complex chiral superstructures. Control and manipulation of the chiral ordering is essential in the development of functional electro-optic devices. Here, the effect of surface topography is combined with an applied electric field to steer the directional growth of cholesteric fingers in a cell with thickness larger than the chiral pitch. The periodic e-beam resist grating gives rise to micrometer-scale periodic variations of the surface anchoring. By applying a voltage to the cell, controlled growth of cholesteric fingers along the surface grating is observed. The 2D liquid crystal director configuration at different voltages is identified by numerical simulations based on finite element Q-tensor theory. The results demonstrate that samples with modulated surface chemistry lead to enhanced control over the formation of chiral structures. This can stimulate the development of electro-optic devices (diffraction gratings, lasers, displays, etc.) with improved characteristics.