Final Report Summary - ACTIVEDYNAMICS (Dynamics of Active Suspensions)
PART A: Methodology establishment
PART B: Dynamics of active suspensions in 3D
PART C: Dynamics of active suspensions in polymer solution in 3D
The success of investigating the collective dynamics of active suspension (dense active suspension) is first based on the development of a careful methodology (Part A) and the understanding of the dynamics of dilute active suspensions (partly Part B and C). The researcher has successfully developed a careful protocol and methodology to investigate the dynamics of suspensions of swimming bacteria as function of bacterial concentration and polymer concentration. Several key results have been obtained. First, a detailed experimental investigation of the dynamics of tracer particles (non-motile bacteria) in a bath of swimming bacteria has been done in three-dimension for the first time. In addition, a theory, based on hydrodynamic interactions considering the flow field created by swimming bacteria, has been developed that allows a quantitative description of the experimental data. Secondly, an extensive investigation of bacteria swimming in polymer solution has been performed. This has brought new insights in our understanding of microorganisms swimming in complex polymeric environment, e.g. bacteria swimming in intestinal mucus. Thirdly, the methodology developed primarily for swimming bacteria during this project has also been applied successfully to other i) microorganisms such as swimming algae, sperm cells, or synthetic self-propelled particles such as active Janus particles; and ii) systems with anisotropic dynamics, e.g. magnetic colloidal suspensions or magnetotactic bacteria. These results have brought interests from not only a broad area of academic science but also industrial research.