Thin film lubrication for large colloidal particles: Experimental test of the no-slip boundary condition

Abstract

We have measured the hydrodynamic force between a particle (R ≈10 μm) and a smooth, flat plate using Atomic Force Microscopy in Newtonian, concentrated sucrose-water solutions for both hydrophilic solids (hydroxyl-terminated silica) and hydrophobic solids (methyl-terminated silica or graphite). For all cases, the measured force is consistent with Reynolds lubrication theory with the no-slip boundary condition and a constant viscosity. Our error in determining the slip length varies according to the particular experiment, but is about 2 nm. We have restricted our analysis to conditions where Reynolds lubrication is valid, i.e., films that are much greater than the molecular diameter of the fl..