Motion of a colloidal particle in a nonuniform director field of a nematic liquid crystal

We investigate the dynamics of a single spherical particle immersed in a nematic liquid crystal. A nonuniform director field is imposed on the substrate by a stripe alignment pattern with splay deformation. The particle of homeotropic anchoring at the surface is accompanied by hyperbolic hedgehog or Saturn-ring defects. The particle motion is dependent on the defect structure. We study the two types of motions theoretically and confirm the obtained results experimentally. The particle accompanied by a hyperbolic hedgehog defect is pulled to a deformed region to relax the elastic deformation energy. The motion occurs in the direction heading the hyperbolic hedgehog defect of a particle in a twist region. The position exhibits a weak S-shaped change as a function of time. The particle accompanied by a Saturn-ring defect shows insignificant motion due to its relatively small deformation energy.