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Wetting hysteresis and dynamics : interpreting dissipation mechanisms at the contact line
A liquid moving over a solid substrate is an everyday occurrence, and the hysteresis and dynamics of the three-phase contact line have been measured in innumerable experiments over the years. In addition, the ingredients needed to describe the phenomenon are known : in the most basic picture, there is viscous dissipation in the bulk of the liquid meniscus, and a dissipation that occurs at the nanometer scale, in the vicinity of the contact line. The latter is often attributed to thermally activated hopping of the contact line over heterogeneities on the surface, which are also implicated in the observation of contact angle hysteresis. Despite this, a unified description taking all of this into account is lacking and extracting meaningful parameters from experiments remains a challenge. In this talk I will describe our approach to disentangle bulk viscous dissipation and dissipation at the contact line in order to interpret our measurements. We perform experiments on well-characterised surfaces with either nano-scale defects or molecular coatings and attempt to link the observed hysteresis and dynamics to measureable surface properties.