HDR defense by Cyril Picard

On the 24th of January 2024, Cyril Picard has defended his HDR entitled "On the edge of continuity"


Confined fluids have been the common thread running through my research for the past ten years. In particular, they play a major role in freshwater production processes using seawater desalination, and in reverse processes designed to recover non-intermittent renewable energy, referred to as osmotic energy. At the heart of these systems are the phenomena of selective solvent and solute transport under confinement. Work carried out in the field today known as nanofluidics has elucidated some of the physical mechanisms involved, based on the experimental use of specific confining materials (e.g. graphene, boron nitride, nanotubes…) This exploration has remained mainly limited to the case of single-phase transport. It is also subject to a number of instrumental constraints. For instance, measuring the tiny flow rate through a nanopore is still a challenge.


In the first part of my talk, I will present the work we have carried out at LIPhy to meet this challenge.

Beyond single-phase situations, the central part of my talk will be dedicated to the study of wetting in nanometric to subnanometric pores. To this end, an original dynamic porosimetry approach has been employed to characterise forced imbibition and drying processes in hydrophobic organised nanoporous structures. In this context, the contribution of line tension, characteristic of the free energy of the contact line, and its possible alteration by surfactants will be discussed.

The last part of my presentation will focus on the impact of solutes and the insights that a new dynamic calo-porosimetric measurement method could provide. I will also outline two avenues being explored in the laboratory as new ways of harvesting osmotic energy, based on the control of transport in fluid media on the edge of continuity.