Shape induced segregation and anomalous diffusion of particles under confinement

Diffusive behaviors in confined environment is a fundamental problem that finds applications in various areas of science and engineering, including cells, supercooled liquids, and mesoporous materials, etc. These behaviors should intuitively be affected by particle shapes and concentrations. However, these effects remain poorly understood due to the computational difficulties in solving hydrodynamic interactions (HIs) between arbitrarily shaped particles in confined space. Here, an immersed boundary–General geometry Ewald-like method (IB-GgEm) is adopted to simulate the dynamics of a mixture of particles of different shapes and relative concentrations with the consideration of both short- and long-range fluctuating HIs. We find that increasing the fraction of cylinders induces particle segregation, where the spherical particles are pushed towards the wall, while the cylinders prefer to be near the center of the cavity. In addition, increasing the fraction of cylinders also affects the diffusive-to-anomalous transition and the degree of anomaly. We believe that our results offer a pathway to understanding fundamental questions in biology, e.g., anomalous macromolecular diffusion in cells, and serve as a route to design and optimize drug-delivering platforms.