PhD: Study of the equilibrium and the transport of electrolytic solutions in confinement - Dandara Velasco

Blue Energy is the term given to the energy generated by the salinity difference between two bodies of water. An osmotic process allows the conversion of this energy into electricity, from the ion flow through membranes like in PRO or RED energy harvesting processes. The estimated power to be produced from Blue Energy in the world is equivalent to 1000 nuclear plants. However, the power density of current technologies is too low to make the process cost-effective and technically viable.

From a physical point of view, this issue falls within the general theme of energy conversion in nanofluidics. These conversions are based on the coupling between hydrodynamics, electrokinetics and the transport of ionic species. These couplings obviously depend on the properties of the confined fluids but also on the equilibrium characteristics of the systems such as the surface charge. To our knowledge, there is no experiment allowing simultaneous measurements of the transport and equilibrium properties of a nanofluidic system.

In this manuscript, the instrumental development of a dynamic Force Surface Apparatus is presented. This machine and its surrounding have been adapted to study electrolyte solutions confined throughout five orders of magnitude (10 μm to 1 Å), with a strict environ- mental control. Experiments were performed on NaCl aqueous solutions, confined between Borosilicate glass or Boron Nitride coated glass surfaces. We have shown the existence of an over-dissipation induced by ions from electrolytes compared to a classical Newtonian behavior. Preliminary results on the influence of the ionic concentration and surface charge on electrolyte over-dissipation are presented.

Committee:

• Carlos Drummond, CRPP (Bordeaux), rapporteur
• Christophe Ybert, ILM (Lyon), rapporteur
• Marie-Caroline Jullien, IP Rennes, examinatrice
• Hugues Bodiguel, LRP (Grenoble), examinateur

PhD advisors:

Romain Lhermerout, Élisabeth Charlaix, Benjamin Cross, Enric Santanach-Carreras