Elastohydrodynamic lift at a soft wall

TL;DR

This paper experimentally demonstrates that microbeads experience a flow-induced lift near soft polymer-coated walls, confirming elastohydrodynamic predictions and revealing soft lubrication effects relevant to microcirculation.

Contribution

First experimental validation of elastohydrodynamic lift caused by flow-induced deformations of a soft layer at microscopic scales.

Findings

Lift increases with flow strength

Flow-induced deformation matches theoretical models

Evidence of soft lubrication at small scales

Abstract

We study experimentally the motion of non-deformable microbeads in a linear shear flow close to a wall bearing a thin and soft polymer layer. Combining microfluidics and 3D optical tracking, we demonstrate that the steady-state bead/surface distance increases with the flow strength. Moreover, such lift is shown to result from flow-induced deformations of the layer, in quantitative agreement with theoretical predictions from elastohydrodynamics. This study thus provides the first experimental evidence of "soft lubrication" at play at small scale, in a system relevant {\it e.g.} to the physics of blood microcirculation.