Speaker
Description
Active baths are the non-equilibrium equivalent of a thermal bath, comprised of several motile active particles that convert the energy in their surroundings into motion. Understanding the statistical and dynamic properties of an active bath of particles, such as E. coli bacteria, have important implications in uncovering novel far-from-equilibrium physics that are potentially generalisable to a wide range of dense active matter systems. Furthermore, applications harnessing the collective movements of active particles are beneficial, ranging from autonomous carriers of cargo and drug delivery to large-scale micro-robotic assemblies. Our work extends upon previous experiments on active baths to elucidate the influence of rotational dynamics on the collective motion of an active bath of E. coli. We induce a rotational fluid flow in suspensions of these E. coli by controllably rotating a birefringent vaterite probe particle using Rotational Optical Tweezers, ROTs. With machine-learning-based particle tracking, we can measure how the dynamics and interactions of bacteria, such as reciprocity or the initiation of orbiting behaviour, change close to the rotating probe. These measurements are combined with mechanical sensing of the probe through optical tweezers such that we obtain further information about the inter- and intra-particle dynamics in the surrounding fluid. We support our experimental results with simulations of individual bacterial particles moving in a local rotational shear flow. By tracking individual bacteria under systematically varied shear rates and viscosity gradients we can quantify controlling order and organisation at mesoscopic scales.
| I am the presenting author | Yes |
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