Direct measurement of interaction between colloidal particles in nematic liquid crystal

Interparticle force F between two colloidal particles accompanied by hyperbolic hedgehog defects has been studied in nematic liquid crystal by two methods. We have directly measured F as a function of interparticle distance R in the case of two "dipoles" composed of a particle and an accompanied defect aligning parallel to the far-field director. We have confirmed the theoretical prediction that F is proportional to R-4 at longer distance but the magnitude of F is different in two methods. We have also observed that repulsive component emerges at shorter distance.