Domain growth kinetics in active binary mixtures.

Area of Science:

• Physics
• Soft Matter Physics
• Statistical Mechanics

Background:

• Active matter systems exhibit unique collective behaviors not seen in equilibrium systems.
• Motility-induced phase separation (MIPS) is a key phenomenon in active matter, leading to self-organization.
• Understanding MIPS in mixtures is crucial for designing active materials.

Purpose of the Study:

• To investigate the phase separation dynamics in symmetric and asymmetric active binary mixtures.
• To characterize the morphology and scaling behavior of domains during MIPS.
• To determine the influence of mixture composition and relative species activity on phase separation.

Main Methods:

• Utilized a coarse-grained run-and-tumble bacterial model to derive density field evolution equations.
• Employed Euler discretization for solving the evolution equations and simulating phase separation dynamics.
• Analyzed domain morphology using equal-time correlation functions (C(r, t)) and structure factors (S(k, t)).

Main Results:

• Observed dynamical scaling in both C(r, t) and S(k, t), indicating self-similar domain growth.
• Demonstrated that scaling function forms are dependent on mixture composition and relative activity (Δ).
• Confirmed diffusive domain growth (L(t) ~ t1/3) and Porod's law (S(k, t) ~ k-(d+1)) at large wavevectors for all mixtures.

Conclusions:

• Active binary mixtures exhibit MIPS with universal diffusive growth and scaling behavior.
• Mixture composition and relative activity are critical parameters controlling the MIPS morphology.
• The findings provide insights into the fundamental principles governing self-organization in active complex fluids.