Active colloidal suspensions: Clustering and phase behavior

Abstract

We review recent experimental, numerical, and analytical results on active suspensions of self-propelled colloidal beads moving in (quasi) two dimensions. Active colloids form part of the larger theme of active matter, which is noted for the emergence of collective dynamic phenomena away from thermal equilibrium. Both in experiments and computer simulations, a separation into dense aggregates, i.e., clusters, and a dilute gas phase has been reported even when attractive interactions and an alignment mechanism are absent. Here, we describe three experimental setups, discuss the different propelling mechanisms, and summarize the evidence for phase separation. We then compare experimental observations with numerical studies based on a minimal model of colloidal swimmers. Finally, we review a mean-field approach derived from first principles, which provides a theoretical framework for the density instability causing the phase separation in active colloids.

11 pages, 5 figures

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Cited by in corpus (24)

• Inertial effects of self-propelled particles: from active Brownian to active Langevin motion
• Spontaneous velocity alignment in Motility-induced Phase Separation
• An active approach to colloidal self-assembly
• Entropy production of active particles and for particles in active baths
• Dynamical mean-field theory and weakly non-linear analysis for the phase separation of active Brownian particles
• Light-switchable propulsion of active particles with reversible interactions
• Synchronization in dynamical networks of locally coupled self-propelled oscillators
• Lane formation in a system of dipolar microswimmers
• Active dipole clusters: from helical motion to fission
• Self-assembly of active amphiphilic Janus particles
• Transport of active particles in an open-wedge channel
• Coarsening and clustering in run-and-tumble dynamics with short-range exclusion
• Time-dependent properties of interacting active matter: dynamical behavior of one-dimensional systems of self-propelled particles
• Optimal active particle navigation meets machine learning
• Phase separation of active Brownian particles in two dimensions: Anything for a quiet life
• Static Structure of Active Brownian Hard Disks
• Three-body correlations and conditional forces in suspensions of active hard disks
• A Lattice Boltzmann dynamic-Immersed Boundary scheme for the transport of deformable inertial capsules in low-Re flows
• Rheological similarities between dense self-propelled and sheared particulate systems
• Estimation of the critical behavior in an active colloidal system with Vicsek-like interactions
• Effective forces between active polymers
• Ostwald-like ripening in the two-dimensional clustering of passive particles induced by swimming bacteria
• Conditions for the propulsion of a colloid surrounded by a mesoscale phase separation
• Occurrence of connected clusters in motility-induced phase-separated states of persistent active particles at zero temperature