Effective interactions between inclusions in an active bath

Abstract

We study effective two- and three-body interactions between non-active colloidal inclusions in an active bath of chiral or non-chiral particles, using Brownian Dynamics simulations within a standard, two-dimensional model of disk-shaped inclusions and active particles. In a non-chiral active bath, we first corroborate previous findings on effective two-body repulsion mediated between the inclusions by elucidating the detailed non-monotonic features of the two-body force profiles, including a primary maximum, and a secondary hump at larger separations that was not previously reported. We then show that these features arise directly from the formation, and sequential overlaps, of circular layers (or 'rings') of active particles around the inclusions, as the latter are brought to small surface separations. These rings extend to radial distances of a few active-particle radii from the surface of inclusions, giving the hard-core inclusions relatively thick, soft, repulsive 'shoulders', whose multiple overlaps then enable significant (non-pairwise) three-body forces in both non-chiral and chiral active baths. The resulting three-body forces can even exceed the two-body forces in magnitude and display distinct repulsive and attractive regimes at intermediate to large self-propulsion strengths. In a chiral active bath, we show that, while active particles still tend to accumulate at the immediate vicinity of the inclusions, they exhibit strong depletion from the intervening region between the inclusions, and partial depletion from relatively thick, circular, zones further away from the inclusions. In this case, the effective, predominantly repulsive, interactions between the inclusions turn to active, chirality-induced, depletion-type attractions, acting over an extended range of separations.

12 pages, 14 figures

References in corpus (24)

• Novel type of phase transition in a system of self-driven particles
• The hydrodynamics of swimming microorganisms
• Self-motile colloidal particles: from directed propulsion to random walk
• Motility-Induced Phase Separation
• Physics of Microswimmers - Single Particle Motion and Collective Behavior
• Hydrodynamic attraction of swimming microorganisms by surfaces
• Propulsion of a molecular machine by asymmetric distribution of reaction--products
• Designing phoretic micro- and nano-swimmers
• Hydrodynamics of self-propulsion near a boundary: predictions and accuracy of far-field approximations
• Swarming and swirling in self-propelled polar granular rods
• Green Algae as Model Organisms for Biological Fluid Dynamics
• Ciliary contact interactions dominate surface scattering of swimming eukaryotes
• Dynamics of a Brownian circle swimmer
• Soft Spheres Make More Mesophases
• Tunable long range forces mediated by self-propelled colloidal hard spheres
• Self-Propelled Rods near Surfaces
• Run-and-tumble particles with hydrodynamics: sedimentation, trapping and upstream swimming
• Orientational order in concentrated suspensions of spherical microswimmers
• Run-and-Tumble Dynamics of Self-Propelled Particles in Confinement
• Active Brownian motion in a narrow channel
• Diffusion of Chiral Janus Particles in a Sinusoidal Channel
• Chirality separation of mixed chiral microswimmers in a periodic channel
• Ratchet transport powered by chiral active particles
• From Lumps to Lattices: Crystallized Clots Made Simple

Cited by in corpus (20)

• Phase separation in binary mixtures of active and passive particles
• Collective forces in scalar active matter
• Spontaneous rotation can stabilise ordered chiral active fluids
• Influence of cap weight on the motion of a Janus particle very near a wall
• Inclusions, Boundaries and Disorder in Scalar Active Matter
• Active particles with polar alignment in ring-shaped confinement
• Force generation in confined active fluids: The role of microstructure
• Active fluids at circular boundaries: Swim pressure and anomalous droplet ripening
• Vorticity Determines the Force on Bodies Immersed in Active Fluids
• Confinement-induced alternating interactions between inclusions in an active fluid
• Steady states of active Brownian particles interacting with boundaries
• Universal reshaping of arrested colloidal gels via active doping
• Motility-induced coexistence of a hot liquid and a cold gas
• Kinetic temperature and pressure of an active Tonks gas
• Effective interactions mediated between two permeable disks in an active fluid
• Dynamic Overlap Concentration Scale of Active Colloids
• Asymmetric and Long Range Interactions in Shaken Granular Media
• Negative drag force on beating flagellar-shaped bodies in active fluids
• Active osmotic-like pressure on permeable inclusions
• Effective single component description of steady state structures of passive particles in an active bath