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Diffusioosmotic and convective flows induced by a non-electrolyte concentration gradient

Williams, Ian, Lee, Sangyoon, Apriceno, Azzurra, Sear, Richard P. and Battaglia, Giuseppe (2020) Diffusioosmotic and convective flows induced by a non-electrolyte concentration gradient Proceedings of the National Academy of Sciences.

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Glucose is an important energy source in our bodies, and its consumption results in gradients over lengthscales ranging from the sub-cellular to entire organs. Concentration gradients can drive material transport through both diffusioosmosis and convection. Convection arises because concentration gradients are mass density gradients. Diffusioosmosis is fluid flow induced by the interaction between a solute and a solid surface. A concentration gradient parallel to a surface creates an osmotic pressure gradient near the surface, resulting in flow. Diffusioosmosis is well understood for electrolyte solutes, but is more poorly characterised for nonelectrolytes such as glucose. We measure fluid flow in glucose gradients formed in a millimetre-long thin channel, and find that increasing the gradient causes a crossover from diffusioosmosis-dominated to convection-dominated flow. We cannot explain this with established theories of these phenomena which predict that both scale linearly. In our system, the convection speed is linear in the gradient, but the diffusioosmotic speed has a much weaker concentration dependence, and is large even for dilute solutions. We develop existing models and show that a strong surface-solute interaction, a heterogeneous surface and accounting for a concentration-dependent solution viscosity can explain our data. This demonstrates how sensitive non-electrolyte diffusioosmosis is to surface and solution properties and to surface-solute interactions. A comprehensive understanding of this sensitivity is required to understand transport in biological systems on lengthscales from micrometres to millimetres where surfaces are invariably complex and heterogeneous.

Item Type: Article
Divisions : Faculty of Engineering and Physical Sciences > Physics
Authors :
Williams, Ian
Lee, Sangyoon
Apriceno, Azzurra
Sear, Richard
Battaglia, Giuseppe
Date : 2020
Funders : European Research Council (ERC)
Copyright Disclaimer : Copyright 2020 The Author(s). Published under the PNAS license.
Uncontrolled Keywords : Diffusioosmosis; Convection; Microfluidics
Related URLs :
Depositing User : Clive Harris
Date Deposited : 10 Sep 2020 17:35
Last Modified : 10 Sep 2020 17:35

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