Project Details
Projekt
Dynamic wetting and dewetting of viscous liquid droplets/films on viscoelastic substrates
Subject Area
Statistical Physics, Nonlinear Dynamics, Complex Systems, Soft and Fluid Matter, Biological Physics
Term
since 2019
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 422786086
When a liquid morphology moves over a (visco)elastic substrate, friction forces in the substrate both at the point of largest substrate deformation, i.e. at the three-phase contact line and at the moving interface are key to understanding energy dissipation and shapes of dewetting rims and are expected to impact the mode selection of spinodal dewetting. Unlike liquid substrates, the local deformation of a solid viscoelastic substrate always has a global impact on the state of the substrate and the resulting strains are permanent. This proposal aims at developing mathematical models and numerical algorithms for two-layer systems that couple the hydrodynamic and viscoelastic boundary value problem with appropriate interface conditions including intermolecular interactions that become relevant at the scales of the dewetting experiments, to predict the spinodal mode selection and rupture process and the dynamics and rim shapes of simple liquids dewetting from solid viscoelastic substrates. The elastic properties of the substrate will bridge three orders of magnitude down to about 1 kPa. In particular for the very soft substrates, we expect effects such as demixing that will be captured by the introduction of additional entropic contributions to the possibly non-linear elasticity and by adding a mixing free energy to the total free energy of the soft polymer gel. In parallel, the same questions will be tackled experimentally exploring nanoscopic thin polystyrene films dewetting from polydimethylsiloxane networks imaged by atomic force microcopy. A quantitative comparison of these experimental results as functions of systematically varied viscoelastic properties shall allow for a detailed and fundamental understanding of the underlying physical processes and to confirm or to falsify effects that are still discussed highly controversially in literature. Besides others, this concerns the existence of the so called Shuttleworth effect for the considered experimental system and the potential demixing of cross-linked elastomer matrix from non-cross-linked molecules of the same material, which was not yet observed for stiff substrates and the length scales that will be considered here.
DFG Programme
Priority Programmes
