Brownian dynamics of elongated particles in a quasi-2D isotropic liquid

TL;DR

This study experimentally investigates how elongated particles experience anisotropic viscous drag in a quasi-2D isotropic fluid, confirming theoretical predictions and revealing regime crossovers across various length scales.

Contribution

It provides experimental validation of hydrodynamic theories for elongated particles in quasi-2D fluids and explores the dependence of drag anisotropy on particle length.

Findings

Drag anisotropy increases with particle length-to-Saffman-Delbrück length ratio.

Hydrodynamic regimes transition at characteristic length scales.

Theoretical models accurately describe experimental data across multiple length scales.

Abstract

We demonstrate experimentally that the long-range hydrodynamic interactions in an incompressible quasi 2D isotropic fluid result in an anisotropic viscous drag acting on elongated particles. The anisotropy of the drag is increasing with increasing ratio of the particle length to the hydrodynamic scale given by the Saffman-Delbr\"uck length. The micro-rheology data for translational and rotational drags collected over three orders of magnitude of the effective particle length demonstrate the validity of the current theoretical approaches to the hydrodynamics in restricted geometry. The results also demonstrate crossovers between the hydrodynamical regimes determined by the characteristic length scales.