Permeative flow and the compatability of smectic C zig-zag defects with compressive and dilative regions

Mukai and Nakagawa have predicted that hairpin and lightning defects corres pond to compressive and dilative regions in the smetic C layer structure. W alton et al. have previously used the Helfrich-Hurault effect and an induce d SmA-SmC phase transition to reconfirm the existence of such dilated and c ompressed regions under situations of permeative flow. Tn the present work, flow-induced compression and dilation is used to confirm the first predict ion. Situations of asymmetric zig-zag defect generation are observed and so me possible explanations offered. Situations in which flow is induced by me chanical cell deformation, and where electric field-induced director switch ing leads to material pumping are also discussed.