Unravelling the role of phoretic and hydrodynamic interactions in active colloidal suspensions

TL;DR

This paper investigates how phoretic and hydrodynamic interactions influence the collective behavior of active colloidal suspensions, revealing the impact of these interactions on clustering and aggregation dynamics in active matter systems.

Contribution

It introduces a numerical study of self-propelled diffusiophoretic colloids considering both phoretic and hydrodynamic interactions, highlighting their roles in cluster formation and morphology.

Findings

Cluster phase emerges in chemoattractive conditions.

Hydrodynamics hinders cluster growth and alters morphology.

Interaction characteristics affect collective dynamics.

Abstract

Active fluids comprise a variety of systems composed of elements immersed in a fluid environment which can convert some form of energy into directed motion; as such they are intrinsically out-of-equilibrium in the absence of any external forcing. A fundamental problem in the physics of active matter concerns the understanding of how the characteristics of the autonomous propulsion and agent-agent interactions determine the collective dynamics of the system. We study numerically suspensions of self-propelled diffusiophoretic colloids, in (quasi)-2d configurations, accounting for both dynamically resolved solute-mediated phoretic interactions and solvent-mediated hydrodynamic interactions. Our results show that the system displays different scenarios at changing the colloid-solute affinity and it develops a cluster phase in the chemoattractive case. We study the statistics of cluster sizes and cluster morphologies for different magnitudes of colloidal activity. Finally, we provide evidences that hydrodynamics plays a relevant role in the aggregation kinetics and cluster morphology, significantly hindering the cluster growth.