Shear-induced reaction-limited aggregation kinetics of Brownian particles at arbitrary concentrations

TL;DR

This paper develops a model to understand how shear flow influences the aggregation kinetics of Brownian particles in concentrated suspensions, with implications for colloid science and biochemical reactions.

Contribution

It introduces an effective medium approach within the Smoluchowski framework that accounts for arbitrary concentrations and shear, extending Kramers' theory to include collective hydrodynamics.

Findings

Model accurately predicts increased aggregation rates with concentration.

Experimental data supports the model's validity.

The approach links shear effects to reaction-limited aggregation mechanisms.

Abstract

The aggregation of interacting Brownian particles in sheared concentrated suspensions is an important issue in colloid and soft matter science per se. Also, it serves as a model to understand biochemical reactions occurring in vivo where both crowding and shear play an important role. We present an effective medium approach within the Smoluchowski equation with shear which allows one to calculate the encounter kinetics through a potential barrier under shear at arbitrary colloid concentrations. Experiments on a model colloidal system in simple shear flow support the validity of the model in the range considered. By generalizing Kramers' rate theory to the presence of collective hydrodynamics, our model explains the significant increase in the shear-induced reaction-limited aggregation kinetics upon increasing the colloid concentration.