Phase behaviour and dynamical features of a two-dimensional binary mixture of active/passive spherical particles

Area of Science:

• Physics
• Soft Matter Physics
• Colloidal Systems

Background:

• Understanding the behavior of mixtures containing both active and passive particles is crucial for developing novel materials and understanding biological systems.
• Phase separation and dynamics in such systems are complex, influenced by inter-particle interactions and self-propulsion.

Purpose of the Study:

• To characterize the phase behavior and dynamics of bidimensional mixtures of active and passive Brownian particles.
• To investigate how varying concentrations of passive components influence the system's phase diagrams and particle dynamics.
• To elucidate the mechanisms by which active particles affect the motion and diffusion of passive particles.

Main Methods:

• Evaluation of state diagrams at different concentrations of passive components.
• Computation of the long-time diffusion coefficient for both active and passive species.
• Analysis of the displacement's probability distribution function to understand dynamics.

Main Results:

• Passive agents generally hinder phase separation, while active agents promote crystal-like structures in passive colloids.
• Active particles induce enhanced activity and super-diffusive behavior in passive particles.
• An inflection point in active particle diffusivity and a maximum in passive particle diffusivity were observed at the onset of the motility-induced phase separation (MIPS) state.

Conclusions:

• Active particles significantly alter the dynamics and phase behavior of passive particles in bidimensional mixtures.
• The study provides insights into the interplay between self-propulsion and passive interactions in driving collective phenomena.
• The observed changes in diffusivity at the MIPS transition highlight the critical role of active particle dynamics in the mixture's overall behavior.