Figure 13.

Mobility coefficients in the radial (μ_∥) and azimuthal (μ_⊥) directions (in arbitrary units) extracted from two-particle microrheology. In the surface-dominated regime (Bq ≫ 1 or d ≪ 1), both coefficients decay logarithmically with distance, following (3.112). In subphase-dominated cases (Bq ≫ 1 or d ≪ 1), the coefficients decay as 1/r and 1/r². The symbols correspond to two-particle displacement correlations along the line of centers (filled symbols) and perpendicular to it (empty symbols), and the solid lines are fits to (3.109). The shapes of the symbols correspond to different surface viscosities. Adapted from Prasad et al. (2006).