Advective-diffusive spreading of diffusiophoretic colloids under transient solute gradients.
basic_science · Level V
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- Record sourced from PubMed, PMID 31777903.
- Also identified by DOI 10.1039/c9sm01938c.
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Abstract
We analytically calculate the one-dimensional advective-diffusive spreading of a point source of diffusiophoretic (DP) colloids, driven by the simultaneous diffusion of a Gaussian solute patch. The spreading of the DP colloids depends critically on the ratio of the DP mobility, M (which can be positive or negative), to the solute diffusivity, D<sub>s</sub>. For instance, we demonstrate, for the first time, that solute-repelling colloids (M < 0) undergo long-time super-diffusive transport for M/D<sub>s</sub> < -1. In contrast, the spreading of strongly solute-attracting colloids (M/D<sub>s</sub>≫ 1) can be spatially arrested over long periods on the solute diffusion timescale, due to a balance between colloid diffusion and DP under the evolving solute gradient. Further, a patch of the translating solute acts as a "shuttle" that rapidly transports the colloids relative to their diffusive timescale. Finally, we use numerical computations to show that the above behaviors persist for three-dimensional, radially symmetric DP spreading. The results presented here could guide the use of DP colloids for microscale particle sorting, deposition, and delivery.