Squeeze film lubrication in silicone oil: Experimental test of the no-slip boundary condition at solid-liquid interfaces

Abstract

The hydrodynamic force between a spherical glass particle (radius ∼ 10 μm) and a smooth, flat glass plate in Newtonian silicone oil (viscosity, η ∼ 95 mPa s) was measured using the atomic force microscopy (AFM) colloidal probe technique and was compared to Reynolds lubrication theory. When the particle and plate were coated with a hydrophobic silane, the measured forces were consistent with Reynolds lubrication theory without the need to introduce the concept of a slip length. When the particle was hydrophilic, the results were more variable, sometimes being consistent with the no-slip boundary condition and sometimes being better fitted by invoking a constant slip length (up to 33 nm). The ..