Laurent Joly (Institut Lumière Matière, Université Lyon 1) présentera mardi 26 septembre à 11h, dans la salle des Conseils de la faculté de Chimie (32.42.101), un séminaire intitulé :
Molecular views on surface-driven flows
Abstract
Surface-driven flows (also called osmotic flows) are generated at interfaces by various thermodynamic gradients (e.g. electric potential gradient : electro-osmosis, solute concentration gradient : diffusio-osmosis, temperature gradient : thermos-osmosis). They represent powerful tools to manipulate liquids in micro and nanofluidic systems, and play a key role in living systems, in sustainable energies, or in water treatment and desalination processes. Osmotic flows arise from the coupling between hydrodynamics and liquid-wall interactions in the nanometric vicinity of the interface, and yet standard descriptions are usually based on continuum models and liquid-wall interactions only. During this talk I will illustrate with recent work how molecular dynamics simulations can be used to investigate the mechanisms underlying surface-driven flow, and in particular to explore the role of interfacial hydrodynamics.
I will first present a molecular level investigation of electro-osmosis (EO) in a liquid film covered with ionic surfactants [1,2]. I will then present some results on diffusio-osmosis, the flow induced by solute concentration gradients. For neutral solutes, with the example of ethanol in water, I will show that standard models based on liquid-wall interactions can fail to predict the mere direction of the flow, and that interfacial liquid dynamics plays a crucial role [3]. Finally I will say a few words about a recent work on thermos-osmosis, the flow induced by temperature gradients, and show similarly the key role of interfacial hydrodynamics [4]. Overall our results show that it is crucial to account for nanoscale dynamics and molecular effects in order to correctly predict surface-driven flows in micro and nanofluidic systems. This better microscopic knowledge of osmotic flows paves the way for the development of new functionalities or for the optimization of performance in various fields going from sustainable energies to active matter.
References
[1] L. Joly, F. Detcheverry, A.-L. Biance : “Anomalous zeta potential in foam films”, Phys. Rev. Lett. 113, 088301 (2014)
[2] A. Barbosa de Lima, L. Joly, “Electro-osmosis at surfactant-laden liquid-gas interfaces : beyond standard models”, Soft Matter 13, 3341 (2017)
[3] C. Lee, C. Cottin-Bizonne, R. Fulcrand, L. Joly, C. Ybert : “Nanoscale Dynamics versus Surface Interactions : What Dictates Osmotic Transport”, J. Phys. Chem. Lett. 8, 478 (2017)
[4] L. Fu, S. Merabia, L. Joly, submitted
