30/09/2022 – V. Bertin – Particles transport near interfaces

Séminaire IUSTI – 30 sept. 2022 – 11h salle 250

Particles transport near interfaces

Vincent Bertin – Twente Univ., Pays-Bas

In this talk, I will discuss about two different problems involving particle motion near interfaces. In a first part, we focus on elastohydrodynamic lubrication, and analyze the confined motion of a rigid sphere moving close to a soft surface. The hydrodynamic interactions between an oscillating sphere and the deformation of the surface allow us to characterize without contact the complex mechanical response of materials, like viscoelasticity, poroelasticity or capillarity. Furthermore, the elastohydrodynamic coupling gives rise to emerging inertial-like forces, such as a lift that repels sliding particle from the soft surface. In a second part, we will discuss about the diffusion of particles in a shear flow. The coupling between the advection and diffusion across the streamlines enhances the dispersion along the flow with respect to molecular diffusion. This phenomenon is called Taylor dispersion and is the dominant mechanism of transport in a variety of contexts such as nutrient and drug transport, chemical reactions in porous media or in many biological processes. In this work, we focus on the influence of the electrostatic and hydrodynamic interactions between particles and the boundary of a micro channel on the Taylor dispersion. An order of magnitude decrease of the dispersion with respect to the classical theory of Taylor-Aris is found both experimentally and theoretically. This shows that the particle-surface interactions is crucial for describing and controlling particle and solute dispersion at the micro and nanoscale.