Defect-Polymorphism-Controlled Electrophoretic Propulsion of Anisometric Microparticles in a Nematic Liquid Crystal

The nontrivial shape of colloidal particles creates complex elastic distortions and topological defects in liquid crystals and plays a key role in governing their electrophoretic propulsion through the medium. Here, we report experimental results on defects and the electrophoretic transport of anisometric (snowman-shaped) polystyrene particles subjected to an alternating electric field perpendicular to the director in a nematic liquid crystal. We demonstrate that the shape asymmetry gives rise to defect polymorphism by nucleating point or ring defects at multiple locations on the particle and controls the direction as well as the magnitude of the electrophoretic propulsion. Unlike spherical particles, quadrupolar anisometric particles can be transported in multiple directions in the plane perpendicular to the applied field. Our findings provide an alternative degree of freedom in translocating microparticles in liquid crystals for applications in microfluidics, controlled transport, and directed assembly.