Diffusioosmosis-driven dispersion of colloids: a Taylor dispersion analysis with experimental validation

Benjamin M. Alessio, Suin Shim, Ankur Gupta, Howard A. Stone

Research output: Contribution to journalArticlepeer-review

Abstract

Diffusiophoresis refers to the movement of colloidal particles in the presence of a concentration gradient of a solute and enables directed motion of colloidal particles in geometries that are inaccessible, such as dead-end pores, without imposing an external field. Previous experimental reports on dead-end pore geometries show that, even in the absence of mean flow, colloidal particles moving through diffusiophoresis exhibit significant dispersion. Existing models of diffusiophoresis are not able to predict the dispersion and thus the comparison between the experiments and the models is largely qualitative. To address these quantitative differences between the experiments and models, we derive an effective one-dimensional equation, similar to a Taylor dispersion analysis, that accounts for the dispersion created by diffusioosmotic flow from the channel sidewalls. We derive the effective dispersion coefficient and validate our results by comparing them with direct numerical simulations. We also compare our model with experiments and obtain quantitative agreement for a wide range of colloidal particle sizes. Our analysis reveals two important conclusions. First, in the absence of mean flow, dispersion is driven by the flow created by diffusioosmotic wall slip such that spreading can be reduced by decreasing the channel wall diffusioosmotic mobility. Second, the model can explain the spreading of colloids in a dead-end pore for a wide range of particle sizes. We note that, while the analysis presented here focuses on a dead-end pore geometry with no mean flow, our theoretical framework is general and can be adapted to other geometries and other background flows.

Original languageEnglish (US)
Article numberA23
JournalJournal of Fluid Mechanics
Volume942
DOIs
StatePublished - Jul 10 2022

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering
  • Applied Mathematics

Keywords

  • dispersion
  • electrokinetic flows
  • Key words colloids

Fingerprint

Dive into the research topics of 'Diffusioosmosis-driven dispersion of colloids: a Taylor dispersion analysis with experimental validation'. Together they form a unique fingerprint.

Cite this