The slipperiness of dishes washed with detergent is a common daily observation. However, the underlying mechanisms remain insufficiently understood. One source of slipperiness may be the adsorption of surfactant molecules on surfaces, inhibiting mechanical contacts. Surfactant adsorption depends strongly on surfactant charge. We directly probe the effects of both ionic and non-ionic surfactants on the friction coefficients between a glass ball and a flat glass surfaces. Our findings reveal that surfactant self-assembly via charge interactions provides more effective lubrication than hydrophobic surfactant interactions involving nonpolar tails alone. Surfactant adsorption is also influenced by surface topography. Our results show how molecular level effects can affect everyday macroscopic observations.
