Description du sujet de thèse

Nanofluidics explores fluid transport at the nanometer scale and opens up prospects for sustainable and innovative technologies. However, the mechanisms governing liquid-solid friction remain poorly understood, particularly the role of interactions between collective excitations of the fluid and those of the confining material. This project aims to harness disorder to better understand and control nanofluidic transport. The first research axis focuses on the impact of the intrinsic disorder of fluids on friction under confinement. When a liquid is cooled toward its glass transition, it becomes more viscous, yet recent experiments have paradoxically shown that such cooling can reduce friction and accelerate flow at the nanoscale. Using advanced numerical simulations, we will study confined liquids of increasing complexity, ranging from idealized atomic models to molecular liquids incorporating internal degrees of freedom and polarizability. Temperature will be used as a control parameter for the liquid's relaxation spectra in order to elucidate the role of liquid-solid interactions in friction. The second axis concentrates on the influence of disorder on the fluctuations of the confining material. Unlike crystalline solids, disordered materials exhibit specific vibrational properties that can affect friction. In particular, introducing atomic defects in graphene membranes alters their vibrational dynamics and impacts friction with confined fluids. We will characterize this effect using cutting-edge simulations and develop an analytical framework for phonon-induced friction, in collaboration with the Micromégas group at LPENS. These results will be compared with experimental measurements of hydrodynamic friction, where a sudden drop in slip is expected. Finally, exploratory research will investigate the potential of disordered membranes for molecular separation. By designing targeted defects, we aim to develop quasi-2D membranes capable of dynamic separation, inspired by 3D porous materials used in isotopic separation. This project will provide a microscopic understanding of liquid-solid friction mechanisms and pave the way for innovative applications in nanofluidics.

Contexte de travail

The PhD project will take place at the Physics Laboratory of the École Normale Supérieure, located at 24 rue Lhomond, Paris 5th arrondissement. Camille Scalliet has expertise in numerical simulations of disordered liquids and solids, as well as in the development of efficient algorithms. This project will be carried out in close collaboration with the Micromégas group within the same laboratory (LPENS), covering both theoretical and experimental aspects.

Contraintes et risques

This project is theoretical, and therefore has no specific safety conditions or risks.