title: Long-range repulsion of colloids driven by ion exchange and diffusiophoresis.
abstract: Interactions between surfaces and particles in aqueous suspension are usually limited to distances smaller than 1 μm. However, in a range of studies from different disciplines, repulsion of particles has been observed over distances of up to hundreds of micrometers, in the absence of any additional external fields. Although a range of hypotheses have been suggested to account for such behavior, the physical mechanisms responsible for the phenomenon still remain unclear. To identify and isolate these mechanisms, we perform detailed experiments on a well-defined experimental system, using a setup that minimizes the effects of gravity and convection. Our experiments clearly indicate that the observed long-range repulsion is driven by a combination of ion exchange, ion diffusion, and diffusiophoresis. We develop a simple model that accounts for our data; this description is expected to be directly applicable to a wide range of systems exhibiting similar long-range forces.
authors.affiliation: Department of Mechanical Engineering and Institute for Complex Molecular Systems , Eindhoven University of Technology, 5612 AZ, Eindhoven, The Netherlands.
authors.forename: Daniel
authors.initials: D
authors.lastname: Florea
authors.forename: Sami
authors.initials: S
authors.lastname: Musa
authors.forename: Jacques M R
authors.initials: JM
authors.lastname: Huyghe
authors.forename: Hans M
authors.initials: HM
authors.lastname: Wyss
keywords: Nafion; chemotaxis; exclusion zone; solute-free zone; unstirred layer
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