Hydrodynamic Force Measurements: Boundary Slip of Water on Hydrophilic Surfaces and Electrokinetic Effects

The hydrodynamic drainage force of aqueous medium between smooth hydrophilic surfaces was measured with the colloidal probe technique up to shear rates of typically ${10}^4{\mathrm{s}}^{-1\mathrm{}}$. Measured force curves were compared to simulations. To reach agreement between experimental and simulated force curves, the hydrodynamic force had to be fitted with a model allowing for boundary slippage. Boundary slip was characterized by a slip length of $8–9\mathrm{nm}$. Force measurements with charged surfaces could be simulated taking only hydrodynamic and electrostatic double-layer forces into account.