Fig. S5.

(A) Schematics of the 1D FA–ECM model. The integrin force distribution is very sensitive to FA size. For small FAs, integrin force is distributed almost uniformly; regions where integrins are force-free appear when FA size is comparable to 4L_c. The leading edge carries the majority of integrin force, and the size of this highly loaded region is a constant if FA size is much larger than 4L_c. A large FA (≫4L_c) can be divided into two parts based on the magnitude of the integrin force; the effective stiffnesses of the two parts are shown in C. Notice that the horizontal axis in C starts from L ∼ 4L_c. A and C are reprinted with permission from ref. 24, with permission from Elsevier (www.sciencedirect.com/science/journal/00063495). (B) Normalized displacement field (with respect to the maximum displacement) for FA plaque (u_p) and ECM (u_s) for an FA of size 16L_c. Note the size of the region of displacement mismatch between the FA plaque and the ECM is ∼4L_c. (D) At low ligand densities, more active integrins are introduced as ligand density increases because the characteristic length is large (E); at high ligand density, a part of the integrins become inactive and the inactive region becomes larger as ligand density increases because the characteristic length decreases (E). (F) Normalized effective stiffness as a function of ligand density for FAs of 0.1 µm, indicating ligand density has similar biphasic influence on stiffness sensing as FA size.