Electric field driven controllable motility of metal-dielectric Janus particles with boojum defects in thin films of a nematic liquid crystal

Abstract

Creation of tiny self-propelled particles is a subject of intense current interest, and control on their direction of motion is critical for application. We study the effect of electric fields on the metal-dielectric Janus particles inducing boojum defect in thin films of a nematic liquid crystal. In a sharp contrast to the response of boojum non-Janus particles, we show that the boojum Janus particles are self-propelled under the action of an ac electric field, which is applied perpendicular to the director in a planar cell. The particles can be transported along any direction, in the plane of the sample, under a steady field. The direction of motion is controllable by changing the field amplitude and frequency. The particle motility is interpreted based on the symmetry breaking of liquid crystal-enabled electro-osmosis (LCEO) flows. The command demonstrated on the motility is promising for tunable transport and microrobotic applications.