Electrophoresis of metal-dielectric Janus particles with dipolar director symmetry in nematic liquid crystals

Abstract: We study electrophoretic mobility of metal-dielectric Janus particles with dipolar director profile in two nematic liquid crystals (LCs) having same (positive) conductivity anisotropy and opposite dielectric anisotropy. The applied ac electric field is parallel and perpendicular to the director for the positive and negative dielectric anisotropy LCs, respectively. The velocity of the Janus particles in both LCs is significantly higher than that of the non-Janus particles. We map the electroosmotic flow fields surrounding the particles using microparticle image velocimetry ($\mu$-PIV) and show that the flows on the metal hemisphere is stronger than that on the dielectric hemisphere and the pumping of LC along the direction of motion of the Janus particles is more than that of the non-Janus particles. For a given liquid crystal, particles with asymmetric surface properties is useful for enhancing their electrophoretic mobility and activity.