Dislocation mobility in smectic liquid crystals

We measure the edge dislocation mobility in thermotropic smectic compounds by in situ deformation experiments. An array of dislocations is created in a wedged homeotropic liquid crystal cell. As it is well known, the dislocat ions are visible in polarized optical microscopy near the smectic A-C trans ition. Under compression the number of layers adjusts to the sample thickne ss, For slow enough strain variation, we observe the edge dislocations clim b and can measure their mobility. We report here some preliminary observati ons of edge and screw dislocations in smectic liquid crystals and of their dynamics under controlled deformation.