Optically driven liquid crystal droplet rotator

Abstract

In this study, the rotation of liquid crystal droplets induced by elliptically polarized laser light was investigated using optical tweezers. The rotation mechanism was analyzed based on the arrangement of liquid crystal molecules within the droplets. The change in the rotation behavior of nematic liquid crystal (NLC) droplets was evaluated by varying the droplet size. The experimental results were analyzed based on the waveplate effect and light-scattering process. The rotation behavior of cholesteric liquid crystal droplets was examined by varying the droplet size and helical pitch, which was controlled by the chiral dopant concentration. The results are discussed in terms of the selective reflection of the incident beam by the helical structure. The dependence of the rotation frequency on the ellipticity of the incident beam was also studied. The main contribution to the rotation gradually changes from light transmission to reflection with increasing chirality of the droplet. An NLC rotator system was constructed using holographic optical tweezers. Such an optically controllable rotator is a typical micro-optomechanical device. Complex flow fields, including multiple vortex and localized shear fields, were realized at the micron scale.