Hydrodynamic interactions induce anomalous diffusion under partial confinement

TL;DR

This paper reveals that hydrodynamic interactions in partially confined colloidal systems cause an unusual divergence in collective diffusion, driven by the mismatch between the confined particle motion and the unconfined fluid flow.

Contribution

It demonstrates that partial confinement leads to a divergence in the collective diffusion coefficient due to hydrodynamic effects, independent of interparticle forces.

Findings

Divergence in the 2D collective diffusion coefficient

Independence from specific interparticle forces

Distinct from purely 2D fluid transport divergence

Abstract

Under partial confinement, the motion of colloidal particles is restricted to a plane but their dynamics is influenced by hydrodynamic interactions mediated by the unconfined, three--dimensional flow of the embedding fluid. We demonstrate that this dimensionality mismatch induces a characteristic divergence in the two--dimensional collective diffusion coefficient of the colloidal monolayer. This result, independent from the specific interparticle forces in the monolayer, is solely due to the kinematical constraint on the colloidal particles, and it is different from the known divergence of transport coefficients in purely two--dimensional fluids.