论文标题
胶体粒子对的方向依赖性动力学和准二维流体中的Stokes-Einstein关系
Direction-dependent Dynamics of Colloidal Particle Pairs and the Stokes-Einstein Relation in Quasi-Two-Dimensional Fluids
论文作者
论文摘要
流体动力相互作用对于各种流体非常重要，尤其是雷诺数量低的流体，例如微生物和富含颗粒的悬浮液，以及在膜中扩散的蛋白质。不幸的是，尽管远场（渐近）流体动力相互作用在两维和三维中完全理解，但近场相互作用却没有，因此我们仍然缺乏对密集液体悬浮液运动的理解。在这一贡献中，我们通过实验探索了近场中的准二维胶体流体中颗粒之间的流体动力相关性。令人惊讶的是，人体框架中粒子对的测量位移和松弛表现出依赖于方向的动力学，可以定量连接到测量的近场流体动力相互作用。这些发现反过来提出了一种机制，即流体动力学如何以及何时导致无处不在的Stokes-Einstein关系（SER）破裂。我们观察到这种分解，有趣的是，我们表明，沿着水动力相关性最小的方向改善了SER的方向依赖性分解。总的来说，这项工作发现了近场流体动力学对二维流体的运输和动态重组的显着影响。
Hydrodynamic interactions are important for diverse fluids especially those with low Reynold's number such as microbial and particle-laden suspensions, and proteins diffusing in membranes. Unfortunately, while far-field (asymptotic) hydrodynamic interactions are fully understood in two- and three-dimensions, near-field interactions are not, and thus our understanding of motions in dense fluid suspensions is still lacking. In this contribution, we experimentally explore the hydrodynamic correlations between particles in quasi-two-dimensional colloidal fluids in the near-field. Surprisingly, the measured displacement and relaxation of particle pairs in the body frame exhibit direction-dependent dynamics that can be connected quantitatively to the measured near-field hydrodynamic interactions. These findings, in turn, suggest a mechanism for how and when hydrodynamics can lead to a breakdown of the ubiquitous Stokes-Einstein relation (SER). We observe this breakdown, and interestingly, we show that the direction-dependent breakdown of the SER is ameliorated along directions where hydrodynamic correlations are smallest. In total, the work uncovers significant ramifications of near-field hydrodynamics on transport and dynamic restructuring of fluids in two-dimensions.
