Three-dimensional analysis of thermo-mechanically rotating cholesteric liquid crystal droplets under a temperature gradient

Abstract

We studied the rotational motion of cholesteric liquid crystal droplets under a temperature gradient (the Lehmann effect). We found that different surface treatments, planar and homeotropic anchoring, provided three types of droplets with different textures and geometries. The rotational velocity of these droplets depends differently on their size. Determining the three-dimensional structures of these droplets by the fluorescence confocal polarizing microscopy, we propose a phenomenological equation to explain the rotational behavior of these droplets. This result shows that the description by the Ericksen-Leslie theory should be valid in the bulk of the droplet, but we need to take into account the surface torque induced by temperature gradient to fully understand the Lehmann effect.