Studying the near-wall hindered diffusion of a particle suspended in a fluid is critical for understanding other more complex, confined systems. We provide a review of the previous experimental and simulation efforts trying to verify the classic calculations in hydrodynamics by Brenner and Faxen. We discuss some of the challenges of extracting the hindered diffusion constants by experiment and simulation. We find that the change in the diffusion constant in the perpendicular direction calculated in MD is roughly consistent with the hydrodynamic result by Brenner provided that they are normalized by the diffusion constant at the center between the two walls. However, the discrepancy grows large when the colloidal particle is very close to the wall where molecular details matter. Even though the agreement can be considerably improved when the attractions between the particles are made stronger to reduce slip to better fulfill the no-slip condition in MD, we report that there is an underlying difference between the range of the wall interactions with the colloidal particle predicted by MD and hydrodynamics. If time allows, we will also discuss a lesser-known but related topic of hindered diffusion near liquid-liquid interfaces and how depletion forces play an important role in this situation.
1) Chio, C.C.; Tse, Y.-L. S.*, Hindered Diffusion near Fluid-Solid Interfaces: Comparison of Molecular Dynamics to Continuum Hydrodynamics, Langmuir 2020, 36 (32), 9412-9423.
2) Chio, C.C.; Tse, Y.-L. S.*, Patchy Colloidal Particles at the Fluid-Fluid Interface, Soft Matter 2018, 14 (46), 9457 – 9465.
Steve Tse received his PhD in theoretical chemistry under the guidance of Prof. Hans C. Andersen at Stanford University in 2011. During his PhD work, he focused on developing new theories and simulation tools, using statistical mechanics, for studying microscopic molecular motion in stochastic models of liquids with highly cooperative dynamics. After PhD, as a Croucher Fellow at the University of Chicago, he began his postdoctoral work with Prof. Gregory Voth and Prof. Thomas Witten to study the charge transport in both aqueous solutions as well as fuel cell membranes by molecular dynamics simulations. In particular, he developed new reactive multiscale models to understand proton/hydroxide transport. In 2015 Oct, he joined the Chinese University of Hong Kong (CUHK) as Assistant Professor. He was promoted to Associate Professor in 2021 Oct. Since the start of Tse research group at CUHK Chemistry Department, his team has been studying different interfacial systems including air-water and fluid-fluid/solid interfaces. A major theme of the research has been to understand the thermodynamics and the dynamics of these systems and the relationships between the two.