Newman Hugh D, Yethiraj Anand
Department of Physics and Physical Oceanography, Memorial University, St. John's, NL, A1B 3X7, Canada.
Sci Rep. 2015 Sep 1;5:13572. doi: 10.1038/srep13572.
In this work, we use structure and dynamics in sedimentation equilibrium, in the presence of gravity, to examine, via confocal microscopy, a Brownian colloidal system in the presence of an external electric field. The zero field equation of state (EOS) is hard sphere without any re-scaling of particle size, and the hydrodynamic corrections to the long-time self-diffusion coefficient are quantitatively consistent with the expected value for hard spheres. Care is taken to ensure that both the dimensionless gravitational energy, which is equivalent to a Peclet number Peg, and dipolar strength Λ are of order unity. In the presence of an external electric field, anisotropic chain-chain clusters form; this cluster formation manifests itself with the appearance of a plateau in the diffusion coefficient when the dimensionless dipolar strength Λ ~ 1. The structure and dynamics of this chain-chain cluster state is examined for a monodisperse system for two particle sizes.
在这项工作中，我们利用重力作用下沉降平衡中的结构和动力学，通过共聚焦显微镜研究存在外部电场时的布朗胶体系统。零场状态方程（EOS）是硬球，无需对粒径进行任何重新标度，对长时间自扩散系数的流体动力学修正与硬球的预期值在数量上一致。我们注意确保无量纲引力能量（等同于佩克莱数Peg）和偶极强度Λ均为单位量级。在存在外部电场的情况下，形成了各向异性的链 - 链簇；当无量纲偶极强度Λ~1时，这种簇的形成表现为扩散系数出现一个平台。针对两种粒径的单分散系统，研究了这种链 - 链簇状态的结构和动力学。
