Izaki Kuniyoshi, Kimura Yasuyuki
Department of Physics, School of Sciences, Kyushu University, 6-10-1 Hakozaki, Fukuoka 812-8581, Japan.
Phys Rev E Stat Nonlin Soft Matter Phys. 2013 Jun;87(6):062507. doi: 10.1103/PhysRevE.87.062507. Epub 2013 Jun 20.
We have studied the interparticle force between colloidal particles with three different types of defects in nematic liquid crystal by dual-beam optical tweezers. The force between a dipole (D)- and a Saturn-ring (S)-type particle at large interparticle distance R is proportional to R(-4.95±0.05). The force between a D- and a planar (P)-type particle and that between an S- and a P-type particle are, respectively, proportional to R(-5.04±0.08) and R(-5.78±0.13). The observed dependence of the interparticle force on R at large R is in agreement with that predicted by electrostatic analogy. The topological quadrupole moments for S and P particles are evaluated from experimental data. We have also studied the force curves in oblique arrangement against the far-field director for respective pairs. The experimental force curves at large R quantitatively agree with those predicted by electrostatic analogy, but they always become attractive at small R due to the reorientation and deformation of defects. The force profiles for the S-P pair are also compared with those obtained by the recent numerical simulation.
我们利用双光束光镊研究了向列相液晶中具有三种不同类型缺陷的胶体颗粒之间的颗粒间作用力。在较大颗粒间距(R)时，偶极子（D）型颗粒和土星环（S）型颗粒之间的力与(R^{(-4.95±0.05)})成正比。D型颗粒和平面（P）型颗粒之间的力以及S型颗粒和P型颗粒之间的力分别与(R^{(-5.04±0.08)})和(R^{(-5.78±0.13)})成正比。在较大(R)时观察到的颗粒间作用力对(R)的依赖关系与静电类比预测的一致。根据实验数据评估了S型和P型颗粒的拓扑四极矩。我们还研究了各对颗粒在相对于远场指向矢倾斜排列时的力曲线。在较大(R)时的实验力曲线与静电类比预测的定量一致，但由于缺陷的重新取向和变形，在较小(R)时它们总是变为吸引力。还将S-P对的力分布与最近数值模拟得到的结果进行了比较。
