Dependence of interparticle force on temperature and cell thickness in nematic colloids

Noboru Kondo, Yasutaka Iwashita, and Yasuyuki Kimura

We have experimentally studied the interparticle force between two particles accompanied by hyperbolic hedgehog defects in a nematic liquid crystal. The force F was measured with dual-beam optical tweezers at various temperatures and in cells with various thicknesses. In a thick cell, the dependence of F on the interparticle distance R obtained at different temperatures can be scaled to a universal curve of F∝R−4 for R>3a, where a is the radius of a particle. The effective elastic constant evaluated from F is found to be in good agreement with splay constant of the nematic liquid crystal. In a thin cell, the magnitude of F decreases and the dependence ofF on R becomes short-ranged as the thickness of a cell, L, decreases. The reduced force curves, FL4 against R/L, at different L are found to be scaled to a single theoretical curve which has been proposed recently.

DOI