Collective behavior of thermophoretic dimeric active colloids in three-dimensional bulk

Area of Science:

• Colloid science
• Soft matter physics
• Active matter

Background:

• Phoresis-driven colloids are key to designing synthetic microswimmers.
• The dynamics of these swimmers are significantly shaped by phoretic and hydrodynamic interactions.
• Dimeric Janus active colloids offer a model system to study these complex interactions.

Purpose of the Study:

• To investigate the behavior of dimeric Janus active colloids using explicit solvent simulations.
• To analyze how modifications in phoretic character (thermophilic to thermophobic) and bead size affect fluid dynamics.
• To understand the emergent collective phenomena arising from combined phoretic and hydrodynamic interactions.

Main Methods:

• Explicit solvent simulations of dimeric Janus active colloids.
• Systematic variation of phoretic properties (thermophilic vs. thermophobic).
• Analysis of resulting solvent velocity fields and inter-dimer interactions.

Main Results:

• Phoretic character strongly influences solvent velocity fields, shifting from puller-type to pusher-type flows, though distinct from standard models.
• Thermophilic dimers exhibit attractive phoretic interactions, leading to stable, large aggregate formation.
• Thermophobic dimers show repulsive phoretic interactions, preventing clustering and forming short-lived, aligned swarms due to hydrodynamic forces.

Conclusions:

• The interplay between phoretic and hydrodynamic interactions governs the self-assembly and collective dynamics of Janus active colloids.
• Tuning phoretic properties offers a route to control microswimmer aggregation and swarming behaviors.
• Explicit solvent simulations are crucial for accurately capturing the nuanced dynamics of active colloids.