Motility versus fluctuations in mixtures of self-propelled and passive   agents
  Many biological systems consist of self-motile and passive agents both of which contribute to overall functionality. However, there are very few studies of the properties of such mixtures. Here we formulate a model for mixtures of self-motile and passive agents and show that the model gives rise to three different dynamical phases: a disordered mesoturbulent phase, a polar flocking phase, and a vortical phase characterized by large-scale counterrotating vortices. We use numerical simulations to construct a phase diagram and compare the statistical properties of the different phases of the model with self-motile bacterial suspensions. Our findings afford specific insights regarding the interaction of microorganisms and passive particles and provide novel strategic guidance for efficient technological realizations of artificial active matter. 
Denis F. Hinz, Alexander Panchenko, Tae-Yeon Kim, Eliot Fried
cond-mat.soft physics.bio-ph physics.comp-ph physics.flu-dyn