title: Patterning-induced surface chirality and modulation of director twist in a nematic cell.
abstract: A substrate coated with a polyimide alignment layer is scribed bidirectionally with the stylus of an atomic force microscope to create an easy axis for liquid-crystal orientation. The resulting noncentrosymmetric topography breaks two-dimensional inversion symmetry and results in a spatial amplitude modulation of an imposed twisted nematic state. This is observed optically as spatially periodic light and dark stripes. When the alignment layer is scribed unidirectionally the centrosymmetric topography maintains inversion symmetry, and no stripes are observed. The appearance of the twist modulation is consistent with a chiral term in the free energy.
authors.affiliation: Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106-7079, USA. yxc227@case.edu
authors.forename: Yoonseuk
authors.initials: Y
authors.lastname: Choi
authors.forename: Timothy
authors.initials: T
authors.lastname: Atherton
authors.forename: Sameh
authors.initials: S
authors.lastname: Ferjani
authors.forename: Rolfe G
authors.initials: RG
authors.lastname: Petschek
authors.forename: Charles
authors.initials: C
authors.lastname: Rosenblatt
mesh_terms: D016880:Anisotropy; D003198:Computer Simulation; D050866:Liquid Crystals / Q000737:chemistry*; D008956:Models, Chemical; D008968:Molecular Conformation; D012031:Refractometry; D013499:Surface Properties