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Microfluidic free interface diffusion: Measurement of diffusion coefficients and evidence of interfacial-driven transport phenomena

Abstract : We have developed a microfluidic tool to measure the diffusion coefficient D of solutes in an aqueous solution by following the temporal relaxation of an initially steep concentration gradient in a microchannel. Our chip exploits multilayer soft lithography and the opening of a pneumatic microvalve to trigger the interdiffusion of pure water and the solution initially separated in the channel by the valve, the so-called free interface diffusion technique. Another microvalve at a distance from the diffusion zone closes the channel and thus suppresses convection. Using this chip, we have measured diffusion coefficients of solutes in water with a broad size range, from small molecules to polymers and colloids, with values in the range [Formula: see text] m 2 /s. The same experiments but with added colloidal tracers also revealed diffusio-phoresis and diffusio-osmosis phenomena due to the presence of the solute concentration gradient. We nevertheless show that these interfacial-driven transport phenomena do not affect the measurements of the solute diffusion coefficients in the explored concentration range.
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https://hal-cnrs.archives-ouvertes.fr/hal-03795515
Contributor : jean-baptiste Salmon Connect in order to contact the contributor
Submitted on : Tuesday, October 4, 2022 - 9:59:44 AM
Last modification on : Wednesday, October 5, 2022 - 4:00:12 AM

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Hoang-Thanh Nguyen, Anne Bouchaudy, Jean-Baptiste Salmon. Microfluidic free interface diffusion: Measurement of diffusion coefficients and evidence of interfacial-driven transport phenomena. Physics of Fluids, 2022, 34 (5), pp.052008. ⟨10.1063/5.0092280⟩. ⟨hal-03795515⟩

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