Single polymer adsorption in shear: flattening versus hydrodynamic lift and corrugation effects

TL;DR

This study uses simulations and scaling arguments to explore how shear flow affects single polymer adsorption, revealing that hydrodynamic lift and surface roughness weaken adsorption by causing desorption and reducing surface attraction.

Contribution

It distinguishes the competing effects of shear-induced flattening and hydrodynamic lift on polymer adsorption, highlighting the dominant role of lift in weakening adsorption under shear.

Findings

Hydrodynamic lift causes long-range repulsion, leading to discontinuous desorption.

Shear flow overall weakens polymer adsorption due to lift effects.

Surface corrugations further reduce surface attraction.

Abstract

The adsorption of a single polymer to a flat surface in shear is investigated using Brownian hydrodynamics simulations and scaling arguments. Competing effects are disentangled: in the absence of hydrodynamic interactions, shear drag flattens the chain and thus enhances adsorption. Hydrodynamic lift on the other hand gives rise to long-ranged repulsion from the surface which preempts the surface-adsorbed state via a discontinuous desorption transition, in agreement with theoretical arguments. Chain flattening is dominated by hydrodynamic lift, so overall, shear flow weakens the adsorption of flexible polymers. Surface friction due to small-wavelength surface potential corrugations is argued to weaken the surface attraction as well.