Figure 2.

Modulation of cell spreading area with matrix rigidity. Main panel shows a quantitative fit of the model Eq. 7 to our experimentally measured values for human mesenchymal stem cells; the fit was obtained with the value $E_c^{\prime }=11.5kPa$ and did not include the point corresponding to E_m = 34 kP a due to its large error. The inset shows how the modulation of cell area varies with the cell shape and the rigidity fraction, E_m/E_c. This plot is for η_a = α_v = α_s = 0; cell and matrix Poisson ratios are ν_c = 0.3 and ν_m = 0.45 respectively. For finite values of α_v and α_s the cell area decreases. Finite values of spreading asymmetry, η_a (see Eq. 8 below), have only a small effect on these results.