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Regensburg 2022 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 20: Active Matter 4 (joint session DY/BP/CPP)

BP 20.4: Vortrag

Mittwoch, 7. September 2022, 15:45–16:00, H18

Interfacial activity dynamics of confined active droplets — •Prashanth Ramesh1,2, Babak Vajdi Hokmabad1, Arnold J.T.M. Mathijssen3, Dmitri O. Pushkin4, and Corinna C. Maass1,21Max Planck Institute for Dynamics and Self-Organization — 2University of Twente — 3University of Pennsylvania — 4University of York

Active emulsions exhibit a complex hydrodynamic mode spectrum driven by chemical advection-diffusion instabilities. We study such an active emulsion consisting of oil droplets that dynamically solubilize in a supramicellar aqueous surfactant solution. It has been predicted that the interaction with self-generated chemical fields leads to multistable higher-mode flow fields and chemorepulsive phenomena. To investigate such chemodynamic effects, we study cylindrical droplets pinned between the top and bottom surfaces of a microfluidic reservoir, such that they only produce pumping flows, while we simultaneously quantify the chemical concentration field and the hydrodynamic velocity field. With increasing droplet radius we observe: vortical structures generated by the droplet migrating around the interface, bistability between a dipolar and quadrupolar flow mode, and, eventually, a transition to multipolar modes. We further measured flow fields by particle image velocimetry and compared them to a hydrodynamic model based on a Brinkman squirmer. A simultaneous quantification of the flow fields and oil-filled micelle distribution suggests that a local buildup of chemical products leads to a saturation of the surface, which affects the propulsion mechanism and eventually suppresses all activity.

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