Chemical Patterns for Directed Self-assembly Blue Phase Liquid Crystals with Equilibrated Morophologies*

In this work, we show that geometrically simple chemical patterns, made of alternate stripe-like regions with either homeotropic and planar anchoring, can be used to direct the self-assembly of specific blue-phase lattice orientations in an unprecedented fast kinetics. We further analyze the process latitude of epitaxial BPs as single crystal, i.e., the range of periodicity of the stripe-like pattern that promotes the formation of uniform BPI and BPII over macroscopic scales. We focus our study on the phase morphology and the preferred lattice orientation of BPs on such stripe-like chemical patterns, such as the period of the chemical pattern, its relation to the natural period of the BP unit cell size, the width of the chemically patterned feature, and the free energy, including contributions from the elastic energy and the interfacial energy. A fundamental understanding of the equilibrated morphologies of BPs as a function of these parameters can better serve the current technologies and broaden the potential application of directed self-assembly BPs.