Motility-Induced Phase Separation

Active Brownian particles — dense clusters from self-propulsion alone

Self-propulsion v₀ v₀ = 12

Tumble Rate τ⁻¹ τ⁻¹ = 0.10

Density N = 200

Exclusion σ σ = 10

MIPS (Cates & Tailleur 2015): purely repulsive active Brownian particles phase-separate without any attractive interaction. Mechanism: particles slow in dense regions → accumulate → clusters grow. No equilibrium analog exists. Color encodes local density (blue=dilute, green=dense).