Elastohydrodynamic interactions between a spherical particle and a soft boundary.

The motion of a particle in the vicinity of a soft interface gives rise to elastohydrodynamic forces, due to the coupling between the flow induced by the motion and the deformation of the soft interface. One example is the emergent non-inertial lift force that repels on a particle sliding near a soft surface from the latter. We perform asymptotic calculations of the elastohydrodynamic interactions between a spherical particle and a soft boundary (in the small-deformation limit), generalizing the expressions known for an infinite cylinder. This allows for direct comparison with experiments involving spherical colloids. In particular, we present experimental measurements at the nanoscale of the elastohydrodynamic lift force, using an Atomic Force Microscope in quantitative agreement with the derived asymptotic theory.