Interparticle Potential and Drag Coefficient in Nematic Colloids

Abstract

Magneto-optic tweezers were used for measurements of liquid-crystal-mediated forces between spherical beads with tangential anchoring in thin nematic samples. Repulsive force, which results from the quadrupolar symmetry of defects around the immersed beads, decreases proportionally to $1/x^6$, with $x$ being the bead separation. The velocity with which the particles are pushed apart also follows the same separation dependence. We thus find the effective drag coefficient ${\gamma }_{\mathrm{eff}}$ independent of $x$ for surface-to-surface distances as small as 10% of the bead diameter. DOI: http://dx.doi.org/10.1103/PhysRevLett.96.207801 © 2006 The American Physical Society