Fig. 4: Depletion interaction potential between polystyrene beads in Pluronic F108 (1 mM and 2 mM) water-based (PBS 1X) solutions (T = 40 ^°C).

a, b We show experimental results for U(r) (squares and circles) for two different particle sizes, 2R ≃ 500 nm and 2R ≃ 710 nm. Every experimental dataset was obtained by selecting a distinct pair of particles. Dash-dotted lines show predictions by the Asakura-Oosawa model, calculated using \(U(h) \,=\,-\frac{1}{2}\pi nR{\,(\,{d}_{m}-h)}^{2}\), where n is the number density of the depletant micelles, h is the surface-surface distance. h = 0 sets the contact distance between the particle’s centers d ≃ 2R. We find a best fit for d = 505 nm (1 mM) and d = 502 nm (2 mM) in panel (a) and d = 722 nm (1 mM) and d = 715 nm (2 mM) in panel (b). d_m = 22 nm, the diameter of the depletant micelles, as obtained from dynamic light scattering (DLS). n is calculated from the pluronic F108 concentration assuming an aggregation number of 45 for a best fit. Solid lines show the Asakura-Oosawa model prediction blurred by experimental errors, as described in the methods section.