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, δf, monotonically increases with increasing size difference. The difference δf 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.
Thursday, February 11, 2010
Arrangement dependence of interparticle force in nematic colloids
Takahiro Kishita, Kenji Takahashi, Masatoshi Ichikawa, Jun-ichi Fukuda, and Yasuyuki Kimura
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, δf, monotonically increases with increasing size difference. The difference δf 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.
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, δf, monotonically increases with increasing size difference. The difference δf 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.
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