Probing the Hydrodynamic Boundary Condition from Surface Perturbations in Thin Liquid Films

For flows on the micro- and nanoscale, the hydrodynamic boundary condition of a liquid at a solid surface plays an enormous role. In recent years much has been learned about this slip boundary condition from flows that are driven by capillary forces, e.g.\ dewetting thin liquid films featuring a three-phase contact line [1]. Recently, we have shown that the amplification of surface perturbations in thin liquid films allows for a quantification of slippage in the absence of a contact line [2]. We also show that the opposite approach, i.e.\ the capillary levelling of initially perturbed free surfaces [3], is sensitive to the slip boundary condition at the solid/liquid interface. Thin film models comprising slip enable a quantification of the slip length of viscous liquids of various molecular properties. [1] O. B\"aumchen et al., Phys.\ Rev.\ Lett.\ 113, 014501 (2014). [2] S. Haefner et al., Nature Comm. 6, 7409 (2015). [3] J.D. McGraw et al., Phys.\ Rev.\ Lett.\ 109, 128303 (2012).