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DY: Fachverband Dynamik und Statistische Physik

DY 24: Focus Session: New Trends in Nonequilibrium Physics – Conservation Laws and Nonreciprocal Interactions I

DY 24.10: Talk

Wednesday, March 20, 2024, 12:15–12:30, BH-N 243

Self-excited oscillations and motion of sessile drops covered by autocatalytic surfactants — •Florian Voss and Uwe Thiele — Institute for Theoretical Physics, University of Münster, Germany

We consider shallow sessile drops of a nonvolatile liquid covered by a mixture of surfactants that can transform into each other via a simple autocatalytic conversion reaction. Based on the form of a passive gradient dynamics model for fields with conserved and nonconserved dynamics we develop a fully reciprocal three-field model with two conservation laws that captures coupled droplet hydrodynamics [1] and a chemical reaction [2]. We then drive the mechanically, thermodynamically and chemically reciprocal system permanently out of equilibrium by in- and outfluxes of surfactants controlled by external chemostats. Then, we study the resulting active system using linear stability analysis, numerical continuation and time simulations. As the chemostat driving strength is varied, we find, inter alia, the emergence of surfactant (Turing) patterns, breathing and swaying drop oscillations, and oscillatory self-propulsion.

[1] U. Thiele, A. J. Archer, M. Plapp, Phys. Fluids, 2012, 24, 102107

[2] D. Zwicker, Curr. Opin. Colloid Interface Sci., 2022, 61, 101606

Keywords: autocatalytic surfactants; gradient dynamics; chemo-hydrodynamics; (non-)reciprocity; oscillatory self-propulsion