Regensburg 2019 – wissenschaftliches Programm
CPP 25.50: Poster
Dienstag, 2. April 2019, 14:00–16:00, Poster B1
Simulating the hydrodynamics of droplets on photo-switchable substrates — •Josua Grawitter and Holger Stark — Institut für Theoretische Physik, Technische Universität Berlin, Berlin, Germany
Photo-switchable substrates provide a unique mechanism to manipulate liquid droplets precisely by creating and adapting a heterogeneous wettability landscape. Because droplets respond to changes in the wettability, this is a means to keep them in non-equilibrium and thereby induce new states of dynamic wetting.
We present a boundary element method to determine the Stokes flow inside the droplet with a curved free surface and a flat interface at the substrate, where we apply the Navier boundary condition to permit motion of the contact line. In general, boundary element methods solve integral equations by inverting the discretized integrals of the unknown field variable such as fluid velocity.
In our approach we parametrize the free surface of the droplet by a linear combination of smooth basis functions and, using an automatic differentiation algorithm, we calculate its local metric and curvature. This provides high resolution data for an iterative domain-splitting integration scheme capable of treating singular integrands, which are typical for the boundary element method. Following rigorous validation, we will investigate how droplets respond to specific spatio-temporal wettability patterns that either move or deform the droplet. For example, we will generate directed motion by traveling patterns and vary their properties to maximize droplet speed.