Mechanism of lipid nanodrop spreading in a case of asymmetric wetting

Using the surface enhanced ellipsometric contrast microscopy, we follow the last stage of the spreading of egg phosphatidylcholine nanodroplets on a hydrophilic substrate in a humid atmosphere, focusing on the vanishing trilayer in terraced droplets reduced to coexisting monolayer and trilayer. We find that the line interface between them exhibits two coexisting states, one mobile and one fixed. From there, it is possible to elucidate the internal structure and the spreading mechanism of the stratified liquid in a case of asymmetric wetting, i.e., where the lipid film is made of an odd number of leaflets.