Effect of self-propulsion on equilibrium clustering.

Area of Science:

• Colloid and surface science
• Soft matter physics
• Statistical mechanics

Background:

• Colloidal suspensions with specific interactions form stable clusters.
• Self-propulsion introduces activity into particle systems.
• Understanding active matter behavior is crucial for designing novel materials.

Purpose of the Study:

• Investigate the impact of self-propulsion on equilibrium clustering in colloidal suspensions.
• Characterize the relationship between particle activity and cluster size.
• Develop a theoretical model to explain observed clustering phenomena.

Main Methods:

• Brownian dynamics computer simulations to model particle behavior.
• Analysis of cluster size as a function of self-propulsion speed (activity).
• Development of an equilibrium model incorporating activity-induced interactions.

Main Results:

• Clustering remains stable under self-propulsion.
• Cluster size shows non-monotonic dependence on activity: increasing at low speeds, decreasing at higher speeds.
• Simulations reveal distinct clustering behavior compared to motility-induced phase separation.
• The proposed model semiquantitatively explains simulation results.

Conclusions:

• Self-propulsion does not disrupt equilibrium clustering in these colloidal systems.
• Activity-induced attraction and repulsion, dependent on speed, govern the observed clustering.
• Predictions are experimentally verifiable with synthetic colloidal microswimmers.