Modelling of wetting of soft solid substrates
Develop a completely new physical theory of behaviour of liquid droplets on soft solids taking into account the surface forces action and contact angle hysteresis.
Originality and innovative aspects: There are a number of works where the 3-phase contact line is treated either as a mathematical line (circle) or a slightly redistributed region around a mathematical 3-phase contact line. In the first case there is a singularity of deformations at the mathematical 3-phase contact line. In the second case there is no firm physical reason for existence of the redistributed region in a vicinity of the three phase contact line. It was shown that because of surface forces action in a vicinity of the 3-phase contact line the latter becomes not a mathematical line but a transition zone between the bulk liquid and the thin films in front of the bulk liquid. The action of the disjoining/conjoining (Derjaguin’s) pressure inside the transition zone results in a very special distribution of normal stresses inside this zone. However, there was not a single attempt to calculate self consistently the deformation of the solid caused by the Derjaguin’s pressure action. The computation of deformations is a significant innovative aspect of the present WP in comparison with the state of the art.
Methodologies: A theory of the contact angle hysteresis developed recently under consideration of the Derjaguin’s pressure will be combined with the computation of the solid deformation performed using software COMSOL. A collaboration with TUD (WP 1) having a complementary expertise in experimental study of liquid drops on deformable solids is planned.
Risk assessment: The general solution of the problem is extremely challenging due to the high complexity of physical phenomena simultaneously acting at different time and length scales. The possible risk is that the full-scale modelling will be excessively time and resources consuming. The contingency plan is using simplified mechanical models of deformations of soft solids
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