Diffusiophoresis: From dilute to concentrated electrolytes

Ankur Gupta, Suin Shim, Howard A. Stone

Research output: Contribution to journalArticlepeer-review

41 Scopus citations


Electrolytic diffusiophoresis is the movement of colloidal particles in response to a concentration gradient of an electrolyte. The diffusiophoretic velocity vDP is typically predicted through the relation vDP = DDP ∇log cs, where DDP is the diffusiophoretic mobility and cs is the concentration of the electrolyte. The logarithmic dependence of vDP on cs may suggest that the strength of diffusiophoretic motion is insensitive to the magnitude of the electrolyte concentration. In this article, we emphasize that DDP is intimately coupled with cs for all electrolyte concentrations. For dilute electrolytes, the finite double layer thickness effects are significant such that DDP decreases with a decrease in cs. In contrast, for concentrated electrolytes, charge screening could result in a decrease in DDP with an increase in cs. Therefore, we predict a maximum in DDP with cs for moderate electrolyte concentrations. We also show that for typical colloids and electrolytes , where Ds is the solute ambipolar diffusivity. To validate our model, we conduct microfluidic experiments with a wide range of electrolyte concentrations. The experimental data also reveals a maximum in DDP with cs, in agreement with our predictions. Our results have important implications in the broad areas of electrokinetics, lab-on-a-chip, active colloidal transport and biophysics.

Original languageEnglish (US)
Pages (from-to)6975-6984
Number of pages10
JournalSoft matter
Issue number30
StatePublished - Aug 14 2020
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • General Chemistry
  • Condensed Matter Physics


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