Motility-Induced Phase Separation
Active Brownian Particles (ABPs) self-propel at speed v₀ = Pe·D/σ and undergo rotational diffusion with rate D_r. The persistence length ℓ = v₀/D_r sets the scale of directed motion.
Unlike equilibrium systems, activity alone drives MIPS: dense clusters form because fast particles brake in crowds (local density slows self-propulsion via steric repulsion). No attractive forces needed — pure non-equilibrium effect (Cates & Tailleur, 2015).
The MIPS binodal lies roughly at Pe ≳ 40 for ρ ≳ 0.2. Dense clusters coexist with a dilute active gas.
active matter
MIPS
non-equilibrium
Cates-Tailleur