Meniscus and Dislocations in Free-Standing Films of Smectic-<i>A</i>Liquid Crystals

Abstract

A flat, freely suspended film of smectic-A liquid crystal supports a pressure difference, \ensuremath{\Delta}p, across its two free surfaces. The size of its meniscus is about 10 \ensuremath{\mu}m, 2 orders of magnitude smaller than the capillary length, and its profile is predicted to be circular, in accordance with our measurement. The measurement of its radius of curvature gives \ensuremath{\Delta}p. We nucleate ex nihilo an elementary edge dislocation loop, and from its critical radius and growth dynamics (governed by \ensuremath{\Delta}p), we find the line tension $(\ensuremath{\sim}8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}\mathrm{dyn})$ and the mobility of an elementary edge dislocation $(\ensuremath{\sim}4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}{\mathrm{cm}}^{2}\mathrm{s}/\mathrm{g})$.