Aggregation and sedimentation of active Brownian particles at constant affinity

Area of Science:

• Soft Matter Physics
• Chemical Physics
• Statistical Mechanics

Background:

• Active particles exhibit motility-induced phase separation (MIPS).
• Particle propulsion speed is often assumed constant, but can vary with local environment.
• Interplay between particle interactions and propulsion dynamics is crucial for MIPS.

Purpose of the Study:

• Investigate the impact of non-constant propulsion speed on MIPS.
• Analyze how propulsion speed variations, linked to inter-particle forces, affect collective behavior.
• Examine the influence of non-constant propulsion on sedimentation profiles.

Main Methods:

• Theoretical modeling of active particle systems.
• Utilizing ideal reservoirs (chemostats) to control chemical species interconversion.
• Simulations and analytical calculations for hard and soft disc models.

Main Results:

• Non-constant propulsion, driven by inter-particle forces, enhances MIPS feedback.
• For hard discs, MIPS is primarily governed by average propulsion speed.
• Soft particles at high propulsion speeds show significant deviations in collective behavior due to variable propulsion.

Conclusions:

• Variable propulsion speed is a key factor in MIPS, especially for soft active matter.
• The study highlights the importance of considering dynamic propulsion in active matter theories.
• Non-constant propulsion influences both phase separation and sedimentation phenomena.