Description du sujet de thèse

Confined water is omnipresent in nature. It plays a crucial role in the biochemical processes of living organisms, but also in various phenomena at the nanometric scale that are fundamental to addressing several major societal challenges, such as freshwater supply, provided in many parts of the world by desalinating seawater, and the defossilization of our energy resources by instead harnessing the mixture of fresh river water and seawater in estuaries. This non-intermittent energy source, known as osmotic energy [1], has been listed in the European Renewable Energy Directive since 2022.

In this context related to water and energy applications, fundamental research in nanofluidics aims to understand coupled transport phenomena, mainly mass, solute, and ion current transport at the nanoscale. However, heat transport and, more broadly, the specific thermal effects at these scales have remained in the shadows, even though their role is significant.
This is the context for this thesis project, funded by the Franco-Brazilian ANR project HTD-PoM, which aims to explore the mechanical and thermal phenomena subsequent to the confinement of aqueous solutions in hydrophobic nanopores. This experimental work will be comprised three points : the study of the subtle coupling between osmotic energy and thermal energy, the characterization of the thermoelastic properties of confined fluids, and finally the exploration of the thermal conductivity of nanoporous materials as a function of their content. Some nanoporous materials are exceptional thermal insulators. We recently predicted a surprising behavior numerically: a lowering of thermal conductivity when the particles are filled with liquid, contrary to what is observed at the macroscopic scale (everyone knows that wet clothing is less insulating and promotes heat transfer). Does the experiment confirm this prediction? Your thesis will help answer this question.

More specifically, the work will be based on an original experimental approach using ordered hydrophobic nanoporous particles immersed in water or an aqueous solution. Forced filling is achieved by pressurizing the liquid to several hundred bars, while drying occurs spontaneously when the pressure is released. The experimental setup allows for the detailed characterization of the pressures and temperature variations characteristic of the filling and emptying processes, depending on the duration of these processes, which is controlled by the setup over four decades of time [2]. These mechanical and thermal measurements are macroscopic signatures of the wetting and drying phenomena at work at the nanometric or even sub-nanometric scale within the pores, phenomena whose study has remained marginal in the field of nanofluidics.

This thesis will be carried out in conjunction with numerical work as part of the HTD-PoM project and will also contribute to an applied project at the laboratory dedicated to an innovative approach to osmotic energy recovery [3].
Candidates must have a solid background in physics, soft matter, and thermodynamics, as well as a keen interest in physical chemistry. More generally, the candidate must be comfortable with interdisciplinarity and motivated by instrumentation and experimental challenges!


[1] B. E. Logan and M. Elimelech. Membrane-based processes for sustainable power generation using water. Nature, 488.7411 (2012)
[2] L. Michel et al. A Dynamical calo-porosimeter to characterize wetting and drying processes in lyophobic nanometric pores, Rev. Sci.
Instrum. 95.10 (2024)
[3] C. Picard, E. Charlaix, and W. Chèvremont. Procédé de conversion d'énergie osmotique en énergie hydraulique et de dessalement,
WO2022/258912.

Contexte de travail

The work will be carried out at the Laboratoire Interdisciplinaire de Physique. The laboratory is a joint CNRS/Université Grenoble Alpes unit. It focuses on the interfaces between physics and other disciplines, in particular life and environmental sciences, mechanics and applied mathematics. The thesis will be carried out within the MODI team (Soft Matter, Organization, Dynamics and Interfaces) as part of research dedicated to nanofluidics and associated societal issues concerning water remediation and the development of new renewable energy sources.

Le poste se situe dans un secteur relevant de la protection du potentiel scientifique et technique (PPST), et nécessite donc, conformément à la réglementation, que votre arrivée soit autorisée par l'autorité compétente du MESR.