Sommaire:

The study of hydrodynamics at increasingly small scales raises fundamental questions about the validity of classical hydrodynamics hypothesis.
Particularly, the sharp interface hypothesis becomes increasingly difficult to verify for nanofluidic systems where the typical size approaches the interface thermal fluctuations length scale. More generally the interplay between macroscopic hydrodynamics and statistical physics at the interface scale is expected to have considerable influence for multi-scales problems. For example, phase-field simulations predict that the viscous dissipation singularity at a moving contact is regularised by evaporation-condensation mechanisms at the interface level.

Following that, here we present an experimental and numerical investigation of the spreading of a sessile droplet for near-critical two-phases liquid mixture. The Tanner's law regime is robustly verified even for droplets close to the critical temperature showing the universality of the viscous spreading. However the system at the droplet scale is thermodynamically unstable and the droplet also shrinks in size. The mechanisms behind this shrinking analogous to evaporation are then explored for spherical aerosols droplets showing gravity and curvature induced diffusion mechanisms. The coupling between spreading and evaporation is then discussed to give a complete picture of the sessile droplet dynamics.

We will then discuss, despite more briefly, an evaporation-driven colloidal skin formation inside an evaporating droplet deposited on superhydrophobic surfaces. The particle's assembly dynamics is explored using molecular dynamics simulations introducing the effect of droplet's evaporation where the skin formation for high Peclet. Strikingly the skin-bulk transition zone can be modeled through a viscous-diffusion balance and shows analogue properties of a phases separating interface but here with a length scale determined by the Peclet number.

Pour plus d'informations, merci de contacter Merindol R.