They demonstrated that bi-layer flows of liquid and gas can result in an over-limiting regime. Namely, a regime in which a higher flow rate of liquid can be achieved as compared to the case when the same liquid flows through the same tube subjected to the same pressure drop and occupies the whole bore. This means that it is possible to release more liquid than predicted by the Poiseuille law, even though in the bi-layer flow liquid does not occupy the whole cross-section.

This paradoxical result is related to the fact, that the less viscous gas layer can flow much faster than the underlying liquid layer and entrain the latter via a significant shear stress. The present results show that the over-limiting liquid flows through nanotubes, seemingly resembling a deviation from the no-slip condition, in reality are entrained by a rapidly moving gas layer in bi-layer liquid/gas flows. This quasi-slip phenomenon happens in relatively large nanotubes (of the order of 500 nm) where the no-slip condition holds with sufficient accuracy. This phenomenon can be beneficial in micro- and nanofluidics, nanoreactors and drug delivery systems, which are the current goals of this team.