Active fluids at circular boundaries: Swim pressure and anomalous droplet ripening

Abstract

We investigate the swim pressure exerted by non-chiral and chiral active particles on convex or concave circular boundaries. Active particles are modeled as non-interacting and non-aligning self-propelled Brownian particles. The convex and concave circular boundaries are used as models representing a fixed inclusion immersed in an active bath and a cavity (or container) enclosing the active particles, respectively. We first present a detailed analysis of the role of convex versus concave boundary curvature and of the chirality of active particles on their spatial distribution, chirality-induced currents, and the swim pressure they exert on the bounding surfaces. The results will then be used to predict the mechanical equilibria of suspended fluid enclosures (generically referred to as 'droplets') in a bulk with active particles being present either inside the bulk fluid or within the suspended droplets. We show that, while droplets containing active particles and suspended in a normal bulk behave in accordance with standard capillary paradigms, those containing a normal fluid exhibit anomalous behaviors when suspended in an active bulk. In the latter case, the excess swim pressure results in non-monotonic dependence of the inside droplet pressure on the droplet radius. As a result, we find a regime of anomalous capillarity for a single droplet, where the inside droplet pressure increases upon increasing the droplet size. In the case of two interconnected droplets, we show that mechanical equilibrium can occur also when they have different sizes. We further identify a regime of anomalous ripening, where two unequal-sized droplets can reach a final state of equal sizes upon interconnection, in stark contrast with the standard Ostwald ripening phenomenon, implying shrinkage of the smaller droplet in favor of the larger one.

15 pages, 7 figures

References in corpus (63)

• Active Particles in Complex and Crowded Environments
• The hydrodynamics of swimming microorganisms
• Self-motile colloidal particles: from directed propulsion to random walk
• The Mechanics and Statistics of Active Matter
• Motility-Induced Phase Separation
• Physics of Microswimmers - Single Particle Motion and Collective Behavior
• Dynamical clustering and phase separation in suspensions of self-propelled colloidal particles
• Athermal Phase Separation of Self-Propelled Particles with no Alignment
• Active Brownian Particles. From Individual to Collective Stochastic Dynamics
• Statistical Mechanics of Interacting Run-and-Tumble Bacteria
• Hydrodynamic attraction of swimming microorganisms by surfaces
• Hydrodynamics of self-propulsion near a boundary: predictions and accuracy of far-field approximations
• Bacterial hydrodynamics
• Pressure is not a state function for generic active fluids
• Growth and Division of Active Droplets: A Model for Protocells
• Circular motion of asymmetric self-propelling particles
• Topographical pathways guide chemical microswimmers
• Scalar ${\varphi }^4$ field theory for active-particle phase separation
• Pressure and Phase Equilibria in Interacting Active Brownian Spheres
• Green Algae as Model Organisms for Biological Fluid Dynamics
• Activity-induced phase separation and self-assembly in mixtures of active and passive particles
• Arrested phase separation in reproducing bacteria: a generic route to pattern formation?
• Dynamics of a Brownian circle swimmer
• Self-propulsion of a catalytically active particle near a planar wall: from reflection to sliding and hovering
• Hydrodynamic capture of microswimmers into sphere-bound orbits
• Towards a 'Thermodynamics' of Active Matter
• Dynamics of Self-Propelled Particles Under Strong Confinement
• Spontaneous symmetry breaking in active droplets provides a generic route to motility
• Negative interfacial tension in phase-separated active suspensions
• Sorting of Chiral Microswimmers
• Active particles with soft and curved walls: Equation of state, ratchets, and instabilities
• Virial pressure in systems of active Brownian particles
• Tunable long range forces mediated by self-propelled colloidal hard spheres
• Detention times of microswimmers close to surfaces: Influence of hydrodynamic interactions and noise
• Theories of Binary Fluid Mixtures: From Phase-Separation Kinetics to Active Emulsions
• Motility-induced phase separation and coarsening in active matter
• Self-Diffusiophoretic Colloidal Propulsion Near a Solid Boundary
• The force on a body in active matter
• Anomalous Thermomechanical Properties of a Self-propelled Colloidal Fluid
• Active vs. Passive Hard Disks Against a Membrane : Mechanical Pressure and Instability
• Swim pressure on walls with curves and corners
• Ideal bulk pressure of active Brownian particles
• Shape and Displacement Fluctuations in Soft Vesicles Filled by Active Particles
• Curvature Induced Activation of a Passive Tracer in an Active Bath
• Active Brownian motion in a narrow channel
• Dynamics and density distribution of strongly confined noninteracting nonaligning self-propelled particles in a nonconvex boundary
• Nonequilibrium dynamics of mixtures of active and passive colloidal particles
• Dynamic self-assembly of microscale rotors and swimmers
• Filling an emulsion drop with motile bacteria
• Mechanical pressure and momentum conservation in dry active matter
• Guiding catalytically active particles with chemically patterned surfaces
• Pattern Formation in Chemically Interacting Active Rotors with Self-Propulsion
• Diffusion of Chiral Janus Particles in a Sinusoidal Channel
• Contractile and chiral activities co-determine the helicity of swimming droplet trajectories
• Dynamics and Separation of Circularly Moving Particles in Asymmetric Patterned Arrays
• Giant adsorption of microswimmers: duality of shape asymmetry and wall curvature
• Droplet Ripening in Concentration Gradients
• Interface stability, interface fluctuations, and the Gibbs-Thomson relation in motility-induced phase separations
• Effective interactions between inclusions in an active bath
• Active depinning of bacterial droplets: the collective surfing of Bacillus subtilis
• Self-Propelled Colloidal Particle Near a Planar Wall: A Brownian Dynamics Study
• Population splitting of rodlike swimmers in Couette flow
• Osmosis with active solutes

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• Active particles with polar alignment in ring-shaped confinement
• Traveling band formation in feedback-driven colloids
• Confinement-induced alternating interactions between inclusions in an active fluid
• Kinetic temperature and pressure of an active Tonks gas
• Effective interactions mediated between two permeable disks in an active fluid
• Active osmotic-like pressure on permeable inclusions