Dresden 2020 – scientific programme
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DY: Fachverband Dynamik und Statistische Physik
DY 2: Active Matter I (joint session BP/CPP/DY)
DY 2.2: Talk
Monday, March 16, 2020, 10:00–10:15, HÜL 386
Light-regulated motility of microbial suspensions induces phase separation in confinement — •Alexandros Fragkopoulos1, Jeremy Vachier1, Johannes Frey1, Flora-Maud Le Menn1, Michael Wilczek1, Marco Mazza1,2, and Oliver Bäumchen1 — 1Max Planck Institute for Dynamics and Self-Organization (MPIDS), D-37077 Göttingen, Germany — 2Department of Mathematical Sciences, Loughborough University, Loughborough, Leicestershire LE11 3TU, United Kingdom
A highly concentrated suspension of self-propelled particles can form large-scale concentration patterns, separating into regions of high and low particle concentrations, due to the activity of the particles and their mutual interactions. However, such a phenomenon has so far been rarely seen in biological systems. Here, we present that a sufficiently concentrated suspension of Chlamydomonas reinhardtii cells, a model organism of puller-type microswimmers, forms such large-scale aggregations under confinement in specific light conditions. We find that cell-cell interactions need to be dominated by collisions for the aggregation to form, resulting to a generic coupling of the cell’s motility and local cell density. In addition, the cell’s motility decreases with decreasing light intensity, which regulates the cell aggregation. Through active Brownian particle simulations, we show that for our system the change of the motility is sufficient to induce the aggregation. Finally, we provide evidence that the photosynthetic activity controls the cell’s motility, and consequentially, the separation of the active suspension into regions of high and low cell density.