Boundary flow of water on supported phospholipid films

We report an investigation of the boundary flow of water on DPPC monolayers and bilayers deposited on Pyrex surfaces, using a dynamic surface force apparatus. We find that a no-slip boundary condition is verified at the water/bilayer interface within 2 nm. In contrast, the interfacial flow properties on monolayers evolve with the time of exposure to water. A significant slip of 10 nm is found on fresh monolayers, which are strongly hydrophobic. The hydrodynamic interaction force with a nearby surface is then significantly reduced over hundreds of nanometers. This slip effect disappears after one day of exposure to water, due to the increased hydrophilicity and roughness of hydrated monolayers.