title: 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.
authors.affiliation: Department of Physics, School of Sciences, Kyushu University, Higashi-ku, Fukuoka 812-8581, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Kishita
authors.forename: Kenji
authors.initials: K
authors.lastname: Takahashi
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Ichikawa
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Fukuda
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Kimura