Precession Mechanism of Nematic Liquid Crystal Droplets under Low Power Optical Tweezers

Abstract

Optical tweezers is a magnificent tool for microscopic manipulation. Owing to few piconewton noninvasive trapping force, the tiny objects from micro sand beads down to living bacteria can be trapped under optical tweezers system. Liquid crystals (LC) are materials that enriched of optical properties providing various phemomena that can be applied for technology. In this report, we applied optical tweezers to nematic liquid crystal system for the optical manipulation study. 5CB (4-cyano-4’-pentylbiphenyl) was used with an appropriate surfactant to prepare nematic liquid crystal (NLC) droplets at room temperature. NLC droplets in radial and bipolar configurations can be formed. They react with light angular momentum and reveal dynamic and static changes through spinning and changing of internal configuration. Several recent articles reported spinning dynamics of NLC droplets under high power trapping (more than a few hundred milliwatts), however, high power caused disturbance in internal configuration of droplets. Dynamic changes of droplet under low power trapping (lower than 100 mW) conducting so far were reported unsuccessful. Here we report the first investigation on behaviour of radial NLC droplet under low power optical trap. The configuration of droplets was not disturbed under low power trapping. We investigated the dynamic behaviour of non-disturbed NLC droplet in low power optical trap.