Mixing and demixing of binary mixtures of active and passive rodlike particles.

Abstract

The segregation behavior of active and passive rodlike particles is investigated in two-dimensional systems with reflective and periodic boundary conditions. The influences of particle aspect ratio, packing fraction, propulsion velocity, and rotational diffusion on segregation are systematically analyzed through particle dynamics simulations. Under reflective boundaries, persistent propulsion and collision-induced alignment, reinforced by wall-induced trapping, amplify activity-driven clustering along the boundaries even at low densities, making segregation stronger and more easily triggered. In contrast, under periodic boundaries, comparable segregation requires sufficiently large propulsion strength, particle anisotropy, and moderate density, as ordering arises purely from collision-induced alignment without wall stabilization. These results highlight the crucial role of boundary effects in controlling anisotropic active-passive segregation and provide a theoretical basis for designing efficient separation and microrobotic systems.