Liquid-Crystal Phase Transitions Induced by Microtextured Substrates

We show that novel orientational states and temperature-dependent tilt angle of the director may be induced in nematic liquid crystals by microtextured substrates, i.e., spatially mixed alignment potentials. In particular, for an alternating stripe pattern of planar and homeotropic substrate potentials, there is a first-order orientational transition between two states with bulk directors orthogonal to each other. This transition can be observed by varying either the temperature or the texturing periodicity, or through the application of an electric field normal to the substrate.