PLANAR NEMATIC ANCHORING ON ROUGH ANISOTROPIC SUBSTRATES - AN ELASTICMODEL

Rough anisotropic substrates, as SiO coated glass plates, can give uni form planar alignment for nematics. We quantify their surface anisotro py by means of the local fractal dimension D calculated from vertical profiles, An elastic model is proposed to explain the existence of the planar nematic easy axis: the elastic strain energy in the bulk of th e nematic depends on D. The nematic aligns along the direction with lo wer D, which imposes the lower deformation. This model should hold for all substrates, with low apparent anisotropy, that can be described a s self-affine surfaces.