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Accueil > Équipes > Matière molle : Organisation, Dynamique et Interfaces > Thèmes de Recherche

Nanofluidic and transport at interfaces

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The phase transition, dynamics and transport of water and electrolyte solutions in nano-pores and/or membranes is of high relevance in new technologies for energy management. We study these issues in poly-electrolyte membranes and solid-states nanopores, with various approach including neutron diffration, spectroscopy, forced wetting, surface force dynamics and electrical measurements.

Transport of water in Soft Porous materials

(M. Plazanet, J. Peters, B. Coasne (PSM team), P. Levitz, L. Michot, A.L. Rollet, G. Meriguet (PHENIX-Paris), D. Qémener, C. Antonelli, M. Semsimilar (IEM, Montpellier), M. Vandamme, J.-M. Pereira, S. Brisard (Laboratoire Navier, Marne la Vallée).

The aim of this project is to provide a predictive description of water transport in soft porous materials. Soft matter is indeed subjected to several interplaying effects that influence transport at the nanoscale : surface heterogeneities due to hydrophilicity/hydrophobicity of the confining surface, diffuse boundary since the penetration depth of water at the surface of the confining matrix is ill-defined, and deformations or mechanical effects such as swelling which are inherent to the soft nature of the host medium and depend on the thermodynamic state of confined water. A correct description of water transport in soft confinement has therefore to consider adsorption and confinement effects, microscopic diffusion mechanisms, and local as well as global host deformations. We therefore propose to develop a unifying framework for water transport in soft porous materials which accounts for coupling between adsorption and deformation.
Our strategy combines well-established experimental, molecular simulation, and theoretical tools to reach this ambitious objective at all relevant length and time scales. The experimental program is based on the complementarity in time and length scales of Neutrons or X-ray scattering (micro scale), NMR (meso scale) and macroscopic permeance measurements. Transport will be characterized on each scale under relevant conditions of stress or strain and pressure gradient of flowing water. The theoretical description will establish two constitutive equations : a first relationship connecting the structural parameters of the membrane (porosity, surface area, pore size) to the mechanical deformation (stress, strain) and a second relationship connecting the structural parameters of the membrane to water transport (permeability). In so doing, we will establish a double structure/property relationship which allows describing the coupling between transport and mechanics through the same common structural parameters of the membrane.
The project is funded by the ANR TWIST.

Water and solutions in hydrophobic nanopores

Forced intrusion and spontaneous extrusion cycles of a nonwetting liquid in a pulverulent nanoporous material with large specific area of the order of 1000 m2/cm3 are envisioned for energy applications. When the pressure is increased, the liquid penetrates into the pores at a well-defined intrusion pressure Pint. The global volume of the system decreases and energy is stored at interfaces. When the pressure is released, the liquid is expelled at an extrusion pressure Pext, lower than Pint for nanometric pores (blue curve of interest for damping application) equal to Pint for sub-nanometric pores (red curve, of interest for reversible energy storage). Sub-nanometric pores can also be used as molecular sieve. With salt solutions, an additional osmotic contribution results from the separation of pure water entering the pore from salt molecules retained out of the pores. This seperation process, in volume, leads to a translation of intrusion/extrusion plateau equal to the osmotic pressure of the solution. Giant osmotic pressure larger than 100 MPa can be sustain beacuse of the « in volume » nature of the extraction.

Dynamic wetting and drying : Nano-meniscii, nanobubbles nucleation
Loic MICHEL, Elisabeth CHARLAIX, Cyril PICARD, in coll. with A. Galarneau at Univ. Montpellier

Hydrophobic nanopores of controlled geometry are an ideal nano-laboratory to study liquid transport in strong hydrophobic confinement. Slow logarithmic dependance of the intrusion and extrusion pressures are observed according to the intrusion or extrusion duration. The dynamical extrusion is controlled by the nucleation of nano-bubbles in hydrophobic environment. We use kinetic studies to determine the critical volume and energy barrier of vapor nucleii in nanopores, and have evidenced the role of line tension in the physics of surface nano-bubbles. Line tension value of the contact line surrounding the nucleation bubble can be measured.

Electrokinetic/nanofluidic transport
(Preeti SHARMA, Elisabeth CHARLAIX, Cyril PICARD and Benjamin CROSS in coll. with L. BOCQUET at ENS Paris)

Below the micrometer scale, flows interact strongly with surfaces. We study the coupling between interfacial hydrodynamics, electro- and diffusio-kinetic transport, and their applications for energy recovery.
This topic is financed by the ANR program Blue Energy, anb by the program ARC -Energy of the Rhône-Alpes-Auvergne region.
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