Lubricated hydrodynamic interactions between a hard spherical indenter and a poroelastic nanolayer

Soft and porous materials are present in a variety of contexts, from physiological or pharmaceutical applications to fundamental physics of interfacial soft matter, while including the example of nanoscale polymer layers. An intermediate layer of a soft material, present between a liquid phase and a solid boundary, can induce remarkable changes in the lubrication mechanics, for example for the motion of a colloidal particle submitted to a given force near this very particular interface . Describing the motility of a microscopic particle in such a context, and adding the porosity of the nearby surface to the elastohydrodynamic coupling, represents a relatively unexplored field. Here, we establish theoretical models and perform numerical simulations for the particle motion. Preliminary experiments with Surface Force Apparatus (SFA) on PNIPAM hydrogel samples are also presented, and applications to Atomic Force Microscopy (AFM) are discussed.