Sessile liquid droplets deposited on soft substrates may cause the substrate deformation and affect the apparent contact angle as well as the spreading dynamics [1-3].
One approach for modelling of these phenomena is a solution of elasticity problem in an infinite half-space under the action of capillary pressure and the concentrated surface tension force applied at the three-phase contact line [4]. This approach requires a definition of a small artificial width, over which the surface tension force is distributed. To avoid this, the concentrated surface tension force has been replaced by a distributed traction based on the disjoining pressure concept [5].
In the present work, dynamic spreading of a droplet over a soft substrate is described in the framework of the disjoining pressure concept. A Finite Element Method for elasticity problem in a substrate is coupled with lubrication approximation for modelling of droplet spreading. The chosen form of disjoining pressure allows an independent definition of contact angle and the thickness of adsorbed layer. Parameter studies are performed to quantify the influence of mechanical properties and size of the substrate, surface tension of the liquid and contact angle on the substrate deformation and spreading dynamics.
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5. White, L. R. J. Colloid and Interface Sci., 258(1): 82-96 (2003).
