<title>Pattern formation in homeotropic nematic induced by mechanical rectilinear and elliptical oscillatory excitation</title>

Abstract

A homeotropic nematic liquid crystal was exposed to low frequency oscillatory shear (Couette flow). In the presence of rectilinear shear a stationary roll pattern was found above a critical amplitude (Ar). In case of elliptical excitation a spatially nonuniform slow rotation of the director was observed, which lead to the propagation of the so called phase waves in two different systems: in a two-phase (nematic-isotropic) system and in a homeotropic nematic layer in the presence of a destabilizing external electric field. Phase waves also have been observed in the ultrasonic frequency range at much smaller shear amplitudes.