Isotropic active colloids: explicit vs. implicit descriptions of propulsion mechanisms

Area of Science:

• Soft Matter Physics
• Colloidal Science
• Chemical Physics

Background:

• Modeling active particles often overlooks many-body interactions crucial for propulsion.
• Understanding collective dynamics in active matter requires explicit consideration of molecular details driving activity.

Purpose of the Study:

• To investigate the collective dynamics of active particles propelled by solute-solute interactions.
• To compare an explicit model accounting for solute dynamics with an implicit model.

Main Methods:

• Utilized a two-dimensional model of isotropic active particles.
• Employed an explicit model simulating microscopic solute dynamics.
• Developed an implicit model with parameters derived from the explicit model at infinite dilution.

Main Results:

• The explicit solute model revealed a strong decrease in the active colloids' diffusion coefficient with increasing density.
• The derived implicit model failed to capture this density-dependent decrease in diffusion.
• This highlights limitations of classical models that decouple pair interactions from activity.

Conclusions:

• Many-body effects stemming from solute-solute interactions significantly impact collective dynamics in active colloidal systems.
• Classical theoretical models neglecting these molecular details are insufficient for accurately describing active matter behavior.
• Accurate modeling of active colloids necessitates incorporating the underlying molecular mechanisms of propulsion and their collective consequences.