Effective squirmer models for self-phoretic chemically active spherical colloids.

Area of Science:

• Colloid Science
• Fluid Dynamics
• Chemical Physics

Background:

• Self-motility of chemically active colloids in Newtonian fluids is often simplified using models of chemical activity and phoretic-slip boundary conditions.
• For simple shapes at low Reynolds numbers, these models map to hydrodynamic squirmers, enabling

Purpose of the Study:

• To illustrate the mapping of chemically active particles to hydrodynamic squirmers within self-diffusiophoresis.
• To demonstrate how the presence of boundaries or other particles alters the behavior of active colloids compared to unbounded fluid models.

Main Methods:

• Modeling chemically active colloids using phoretic-slip hydrodynamic boundary conditions.
• Analyzing particle-particle collisions and behavior near boundaries in self-diffusiophoresis.
• Comparing the dynamics of active colloids with effective squirmer models in unbounded fluids.

Main Results:

• Chemically active particles in unbounded fluids can be effectively modeled as hydrodynamic squirmers.
• The behavior of active colloids near boundaries or in confined geometries deviates qualitatively from effective squirmer predictions.
• Hydrodynamic interactions are strongly dependent on the distribution of chemical species, influencing collective behavior.

Conclusions:

• Simple squirmer models are insufficient for describing the collective behavior and confined dynamics of chemically active colloids.
• Accurate prediction of active colloid dynamics requires explicit consideration of chemical species distribution and its impact on hydrodynamic interactions.
• Understanding emergent behaviors necessitates moving beyond simplified effective models to account for detailed surface chemistry and fluid interactions.