Asakura-Oosawa: entropy-driven effective attraction between large colloids
U_dep (well depth): – kT
Clustering: –
Depletion interaction (Asakura-Oosawa 1954): small depletant particles are excluded from
the gap between large colloids. When colloids approach within σ_d, depletants are expelled,
gaining translational entropy — the entropic gain creates an effective attraction.
Potential: U(r) ≈ -φ_d kT (r < σ+σ_d). Higher depletant concentration → stronger attraction.
Large size ratio → longer range. Drives phase separation into dense/dilute colloidal phases.