Influence of flexoelectricity on electrohydrodynamic instabilities in nematics

We have incorporated the flexoelectric terms in developing one-dimensional models of E.H.D. instabilities in nematics both under D.C. and A.C. excitations. It is shown that, using this model, we can account for the following experimental observations, which could not be adequately explained by earlier models: (i) The observation of oblique rolls whose wave vector q makes an angle α with the undistorted director n ₀, up to some frequency v ₀ in the conduction regime; (ii) the oblique rolls found in the dielectric regime; and (iii) the ‘longitudinal’ E.H.D. instabilities in some systems with negative conductivity anisotropy. We also present some experimental observations under D.C. excitation.