Self-phoretic active particles interacting by diffusiophoresis: A numerical study of the collapsed state and dynamic...

Area of Science:

• Soft matter physics
• Colloidal science
• Active matter

Background:

• Self-phoretic active colloids navigate chemical gradients via diffusiophoresis, similar to bacterial chemotaxis.
• Colloid activity generates effective repulsive and attractive interactions, influencing particle arrangement.

Purpose of the Study:

• To extend the state diagram of active colloid behavior into regions with translational phoretic repulsion.
• To investigate the impact of repulsive forces on dynamic clustering and cluster morphology.

Main Methods:

• Langevin dynamics simulations were employed to model colloid behavior.
• Analysis of cluster size distributions and mean cluster sizes at various area fractions.
• Quantification of cluster kinetics using fusion and fission rate functions.

Main Results:

• Increasing repulsive strength causes collapsed clusters to fluctuate, oscillate, and eventually form static clouds.
• Oscillations are suppressed when phoretic interactions within clusters are not screened.
• A dynamic clustering 2 state was identified as a key signature of phoretic interactions.

Conclusions:

• Phoretic interactions dictate the transition from compact clusters to dynamic colloidal clouds.
• Fusion and fission rates serve as local, measurable indicators of phoretic interactions in single clusters.