Speaker
Description
The collective dynamics of swimming microorganisms is often dictated by long-ranged hydrodynamic interactions, making them an archetypical example of fluid-dominated, “wet” active matter. One example is the collective motion of swimming bacteria that interact through their long-ranged dipolar flow fields to create a stateof so-called “bacterial turbulence” with chaotic, collective swimming with long-ranged orientation correlations. In this talk, I will address several properties of this collective motion, in bulk as well as near interfaces. In 3-dimensional bulk suspensions, I will discuss how enhanced, “giant”, number fluctuations (GNFs), which are a hallmark property of dry active matter systems, become altered in the presence of fluid flows, shedding new light on previous experimental observations of GNFs in bacterial suspensions. In the second part, I will discuss a set of hydrodynamic instabilities arising in microswimmers confined to a 2d plane by a solid or liquid interface. These instabilities correspond to qualitatively novel forms of surface-induced collective motion and microswimmer clustering, in accordance with previous experimental observations.