Laboratoire Matière et Systèmes Complexes

There will be a live diffusion with Zoom.

Monday July 5th, 11h30.

Contact Michael Berhanu to attend the video seminar

How we understand wetting on real surfaces

Kristina Davitt

Laboratoire de Physique de l’Ecole Normale Supérieure (LPENS)

Mechanics, Soft matter, morphogenesis

Ecole normale Supérieure, Paris Sciences & Lettres, Sorbonne-universités, Université de Paris

Abstract : Rain running down a car windshield, butter sloshing around a Teflon pan ; a liquid moving over a solid substrate is an everyday occurrence, yet a complete description of the phenomenon is still lacking. The basic ingredients needed are known – viscous dissipation in the bulk liquid meniscus and a dissipation that occurs at the nanometer scale, in the vicinity of the contact line – but they have not been simultaneously accounted for in a single, coherent picture. The task has been complicated by the fact that in experiments on real surfaces (as opposed to idealised ones), the contribution near the contact line may come from thermally activated hopping of the contact line over the inevitable small scale roughness or chemical heterogeneity present on the solid, or even viscoelastic dissipation in the case of some molecular coatings commonly used in wetting studies. 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. I will describe experiments on well-characterised systems such as controlled nano-scale defects or polymer brushes of variable chain length and attempt to link the observed hysteresis and dynamics to measureable surface properties.