Arrangement dependence of interparticle force in nematic colloids

Abstract

We have experimentally and theoretically studied the interparticle force between two colloidal particles with different sizes accompanied by hyperbolic hedgehog defects in a nematic liquid crystal. The force f was directly measured using dual-beam optical tweezers and calculated theoretically from the equilibrium tensor field around the particles. The dependence of f on the center-to-center distance between particles of different sizes R is different from that for particles with the same size. The magnitude of f depends on the relative arrangement of the particles: f is larger when a defect between the particles belongs to the larger particle. From the theoretical calculation, the difference in f between the two arrangements, deltaf, monotonically increases with increasing size difference. The difference deltaf was experimentally and theoretically found to be proportional to R(-4.6) at large R. The obtained exponent is comparable to the exponent of -5 predicted by electrostatic analogy.