Osmotic traps for colloids and macromolecules based on logarithmic sensing in salt taxis

Palacci JA, Cottin-Bizonne C, Ybert C, Bocquet L. 2012. Osmotic traps for colloids and macromolecules based on logarithmic sensing in salt taxis. Soft Matter. 8(4), 980–994.

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Journal Article | Published | English

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Author
Palacci, Jérémie AIST Austria; Cottin-Bizonne, Cécile; Ybert, Christophe; Bocquet, Lydéric
Abstract
Diffusiophoretic motion of colloids and macromolecules under salt gradients exhibits a logarithmic-sensing, i.e. the particle velocity is proportional to the spatial gradient of the logarithm of the salt concentration, as VDP = DDP∇logc. Here we explore experimentally the implications of this log-sensing behavior, on the basis of a hydrogel microfluidic device allowing to build spatially and temporally controlled gradients. We first demonstrate that the non-linearity of the salt-taxis leads to a trapping of particles under concentration gradient oscillations via a rectification of the motion. As an alternative, we make use of the high sensitivity of diffusiophoretic migration to vanishing salt concentration due to the log-sensing: in a counter-intuitive way, a vanishing gradient can lead to measurable velocity provided that the solute concentration is low enough, thus keeping ∇c/c finite. We show that this leads to a strong segregation of particles in osmotic shock configuration, resulting from a step change of the salt concentration at the boundaries. These various phenomena are rationalized on the basis of a theoretical description for the time-dependent Smoluchowski equation for the colloidal density.
Publishing Year
Date Published
2012-01-28
Journal Title
Soft Matter
Volume
8
Issue
4
Page
980-994
ISSN
eISSN
IST-REx-ID

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Palacci JA, Cottin-Bizonne C, Ybert C, Bocquet L. Osmotic traps for colloids and macromolecules based on logarithmic sensing in salt taxis. Soft Matter. 2012;8(4):980-994. doi:10.1039/c1sm06395b
Palacci, J. A., Cottin-Bizonne, C., Ybert, C., & Bocquet, L. (2012). Osmotic traps for colloids and macromolecules based on logarithmic sensing in salt taxis. Soft Matter. Royal Society of Chemistry. https://doi.org/10.1039/c1sm06395b
Palacci, Jérémie A, Cécile Cottin-Bizonne, Christophe Ybert, and Lydéric Bocquet. “Osmotic Traps for Colloids and Macromolecules Based on Logarithmic Sensing in Salt Taxis.” Soft Matter. Royal Society of Chemistry, 2012. https://doi.org/10.1039/c1sm06395b.
J. A. Palacci, C. Cottin-Bizonne, C. Ybert, and L. Bocquet, “Osmotic traps for colloids and macromolecules based on logarithmic sensing in salt taxis,” Soft Matter, vol. 8, no. 4. Royal Society of Chemistry, pp. 980–994, 2012.
Palacci JA, Cottin-Bizonne C, Ybert C, Bocquet L. 2012. Osmotic traps for colloids and macromolecules based on logarithmic sensing in salt taxis. Soft Matter. 8(4), 980–994.
Palacci, Jérémie A., et al. “Osmotic Traps for Colloids and Macromolecules Based on Logarithmic Sensing in Salt Taxis.” Soft Matter, vol. 8, no. 4, Royal Society of Chemistry, 2012, pp. 980–94, doi:10.1039/c1sm06395b.

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