Regensburg 2025 – scientific programme
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DY: Fachverband Dynamik und Statistische Physik
DY 23: Poster: Active Matter, Soft Matter, Fluids (joint session DY/CPP)
DY 23.18: Poster
Wednesday, March 19, 2025, 10:00–12:00, P3
Coarsening of chemically active droplets — •Stefan Köstler1,2, Yicheng Qiang1, and David Zwicker1 — 1Max Planck Institute for Dynamics and Self-Organization, Am Faßberg 17, 37077 Göttingen, Germany — 2University of Göttingen, Institute for the Dynamics of Complex Systems, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
Droplets formed by phase separation play an important role in cellular organization and are widely used in the design of synthetic cells and lab-on-chip devices. Droplet emulsions typically coarsen due to surface tension and hydrodynamic effects, which generally prevents precise control over droplet sizes. While coarsening can be suppressed by active chemical reactions, it is unclear how these reactions affect the coarsening dynamics and control droplet sizes. To elucidate this, we numerically simulate a binary mixture that phase separates and undergoes reactions. We find three different dynamical regimes: Small droplets are dominated by coalescence due to hydrodynamic advection, then transition to an Ostwald ripening regime dominated by diffusion, and finally exhibit size control by active chemical reactions. We predict the transition from ripening to size control analytically, and we validate our analytical estimate of the final size using a numerical minimization of a surrogate equilibrium free energy. Our theory provides an improved understanding of coarsening mechanisms, allowing to achieve greater control of emulsions.
Keywords: active droplets; phase separation; coarsening; size control; emulsion