Universal Breakup of Colloidal Clusters in Simple Shear Flow

Abstract

ABSTRACT:We have studied the long-term dynamics of shear-induced breakage of individual colloidal clusters, covering a wide range of fractal dimensions, using Stokesian dynamics. We found that the time evolution of the normalized average size of the fragments generated by the breakup process could be scaled using a unique dimensionless time defined by multiplying the real time with the cluster breakage rate constant (τ = t·k B ). Clusters with different masses but the same fractal dimension exhibited almost identical breakage dynamics when exposed to equal overall hydrodynamic forces (ηγR g,0 2 ). The steady-state values of the average size, mass, and standard deviation of fragment mass distribution showed a universal scaling depending only on the overall hydrodynamic force, irrespective of the initial cluster properties. We also identified two asymptotic regimes for the evolution of the fractal dimension, ⟨d f ⟩, of fragments: open clusters (d f ≤ 2

The role of hydrodynamic interactions on the aggregation kinetics of sedimenting colloidal particles

“…This method, coupled with colloidal interactions, thermal motion, and contact mechanics, has been successfully employed to shed light on the rheological behavior of many shear-driven processes, especially shear-thickening. [23][24][25][26] One major problem with SD techniques is their high computational cost, as the building and inversion of the far-field mobility matrix require ( ) and ( ) calculations, respectively (with being the total 𝑂 𝑁 27 and the more recent Fast Stokesian dynamics (FSD) 28 methods, could maintain the same level of accuracy as conventional SD with a lower computational cost that scales as ( ) 𝑂 𝑁 𝑝 𝑙𝑛𝑁 𝑝 and ( ), respectively. However, these operations are still prohibitive for large systems containing 𝑂 𝑁 𝑝 thousands of particles.…”

“…This method, coupled with colloidal interactions, thermal motion, and contact mechanics, has been successfully employed to shed light on the rheological behavior of many shear-driven processes, especially shear-thickening. 23–26…”

Numerical Study of Soft Colloidal Nanoparticles Interaction in Shear Flow

“…These nanoparticles are commonly used in a colloidal system as dispersion of primary particles. However, primary nanoparticles tend to aggregate into large clusters when the system is chemically destabilized or shear flow is applied. − These clusters, when exposed to high enough shear flow, experience a continuous breakup and aggregation until reaching a steady state cluster size. − When the shear rate is low enough or the adhesion between the particles is sufficiently high, the nanoparticles could form a larger aggregate network and create macroscopic porous materials that can be used for various applications . To obtain deeper understanding of the impact of interparticle interactions combined with contact mechanics on the macroscopic properties of formed aggregates, it is necessary to analyze interactions at the level of individual particles.…”

Molecular dynamics simulation of trimer self-assembly under shear

“…[31], higher shear rates eventually led to a non-monotonic effect where clusters became smaller. Although this shear-induced breakup was not observed in this work, this interesting phenomenon may be observed for trimers in future work at higher shear rates than investigated here [54]. Some hypotheses for the mechanism of increased cluster size with increased shear rate are similar to those postulated for nucleating systems under shear: shear may create defects in ordered structures that serve as nucleation sites which encourages further growth, or promotes coalescence [27, 55, 16, 56].…”