Regensburg 2016 – wissenschaftliches Programm
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BP: Fachverband Biologische Physik
BP 61: Anomalous Diffusion in Complex Environments (Focus Session)
BP 61.2: Vortrag
Donnerstag, 10. März 2016, 11:45–12:00, H45
Transport of active Brownian particles in complex environments — •Maria Zeitz and Holger Stark — Institut für Theoretische Physik, Technische Universität Berlin, D-10623 Berlin, Germany
From the perspective of physics, biological microswimmers such as bacteria can be viewed as active particles. Since bacteria often inhabit porous or crowded environments, we examine the dynamics and transport of active particles in a complex environment. We focus on active Brownian particles (APB), which provide a simple model for microswimmers. ABPs have an intrinsic speed and perform rotational as well as translational diffusion.
We study the transport of ABPs moving in a two-dimensional environment of randomly placed and fixed obstacles of a given area fraction φo. For increasing φo we observe a transition from diffusive transport to trapping on long time scales, which happens close to the percolation threshold of the void space 1−φ0≈ 0.67. The behavior on long time scales is universal and depends only on the obstacle density and not on the intrinsic dynamics of the particle. However, on time scales much shorter than the rotational diffusion time, we find ballistic transport and on intermediate timescales we find subdiffusive transport. The crossover times between the three regimes depend not only on φo but also on the details of particle propulsion, e.g. Peclét number.
In a second step we study how obstacles can serve as nucleation seeds for clustering in collective motion of ABPs and therefore promote clogging.