Regensburg 2022 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 31: Active Matter 4 (joint session DY/BP/CPP)

CPP 31.4: Talk

Wednesday, September 7, 2022, 15:45–16:00, H18

Interfacial activity dynamics of confined active droplets — •Prashanth Ramesh^1,2, Babak Vajdi Hokmabad¹, Arnold J.T.M. Mathijssen³, Dmitri O. Pushkin⁴, and Corinna C. Maass^1,2 — ¹Max 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.