Translational and rotational friction on a colloidal rod near a wall

TL;DR

This study uses particulate simulations to analyze how a colloidal rod's translational and rotational friction are affected by proximity to a wall, revealing inverse linear scaling with distance and angular dependence.

Contribution

It provides detailed simulation data on wall-induced friction enhancements for a colloidal rod, including their dependence on distance and orientation, which was previously not well characterized.

Findings

Friction increases near the wall due to hydrodynamic interactions.

Friction enhancement scales approximately inversely with the closest distance to the wall.

Friction depends on the angle between the rod's axis and the wall normal, fitted with polynomial functions.

Abstract

We present particulate simulation results for translational and rotational friction components of a shish-kebab model of a colloidal rod with aspect ratio (length over diameter) $L/D = 10$ in the presence of a planar hard wall. Hydrodynamic interactions between rod and wall cause an overall enhancement of the friction tensor components. We find that the friction enhancements to reasonable approximation scale inversely linear with the closest distance $d$ between the rod surface and the wall, for $d$ in the range between $D/8$ and $L$. The dependence of the wall-induced friction on the angle $\theta$ between the long axis of the rod and the normal to the wall is studied and fitted with simple polynomials in $\cos \theta$.