The effect of surfactant adsorption on liquid boundary slippage

The drainage force between a borosilicate colloid probe and a flat mica surface was measured using a custom-built nanorheology-atomic force microscope, both in pure water and in solutions of a cationic surfactant (cetyltrimethylammonium bromide, CTAB). The previously reported dependence of slip on the local shear rate is suppressed if surfactant molecules are adsorbed on the solid surfaces. Furthermore, when the surfaces are partially covered by surfactant molecules, slip ceases to depend directly on surface wettability, and a similar degree of slippage is measured on hydrophilic and hydrophobic surfaces.