Extended Data Fig. 3: Small amplitude rheology.
From: Dynamic traction force measurements of migrating immune cells in 3D biopolymer matrices
a, Storage modulus derived from frequency sweeps with a cone-plate shear-rheometer at 1% strain amplitude for different collagen concentrations (Batch A, see Extended Data Fig. 2). Dashed lines indicate mean values, and shaded area indicate } one standard deviation. N indicates the number of collagen gels, where each gel was measured in an independent experiment. b, Storage modulus (mean value at 0.02 Hz) scales with collagen concentration according to a power-law with exponent of 1.91 in agreement to previously predicted and measured values69,70. Bars indicate mean }se and dashed line indicates powerlaw fit curve. Individual collagen gels are shown as dots. The sample size is the same as in a. c, Loss tangent δ (loss modulus G″ divided by storage modulus \({G}^{{\prime} }\), averaged between 0.02-2 Hz from the data presented in a) remains below 0.2 for all collagen concentrations,indicating predominantly elastic behavior. d, The FE model parameter k0 (indicating the linear stiffness of the collagen fibers) for different collagen concentrations (see Extended Data Fig. 2) increases approximately linearly with the storage modulus \({G}^{{\prime} }\) of the collagen gels (measured at 0.02 Hz at a strain amplitude of 1% as shown in a). The gray dashed line indicates the predication from continuum mechanics, where k0 =6E, with Young’s modulus E = 2G(1 + v) and Poisson ratio ν = 0.25 for linear elastic, isotropic fiber networks12. Hence, k0 = 15G.
