title: Aggregation and segregation of confined active particles.
abstract: We simulate a model of self-propelled disks with soft repulsive interactions confined to a box in two dimensions. For small rotational diffusion rates, monodisperse disks spontaneously accumulate at the walls. At low densities, interaction forces between particles are strongly inhomogeneous, and a simple model predicts how these inhomogeneities alter the equation of state. At higher densities, collective effects become important. We observe signatures of a jamming transition at a packing fraction ϕ ∼ 0.88, which is also the jamming point for non-active athermal monodisperse disks. At this ϕ, the system develops a critical finite active speed necessary for wall aggregation. At packing fractions above ϕ ∼ 0.6, the pressure decreases with increasing density, suggesting that strong interactions between particles are affecting the equation of state well below the jamming transition. A mixture of bidisperse disks segregates in the absence of any adhesion, identifying a new mechanism that could contribute to cell sorting in embryonic development.
authors.affiliation: Physics Department, Syracuse University, Syracuse, NY 13244, USA. xyang14@syr.edu.
authors.forename: Xingbo
authors.initials: X
authors.lastname: Yang
authors.forename: M Lisa
authors.initials: ML
authors.lastname: Manning
authors.forename: M Cristina
authors.initials: MC
authors.lastname: Marchetti
mesh_terms: D005740:Gases; D008962:Models, Theoretical; D011312:Pressure
chemical_list: D005740:Gases