Fig. 4.

(A) Selected examples of maximum principal stress contour slices along both the migrating cell and the domain of ECM as a function of separation distance from the surface of stiffer ECM in which the cell migrates from three different separation distances of 10 µm, 20 µm, and 30 µm. White meshes on the vertical slice indicate ECM fiber network. Each Inset in A also indicates corresponding separation distance from the surface of stiffer ECM to the centroid of the cell. Here diameter, length, and number of filopodia in three cases are 0.6 µm, 3 µm, and 5, respectively. (B) Corresponding contour plots of maximum principal strain in the domain of ECM. White vectors in the plot indicate displacement vectors at the ECM fiber nodes. (C) Probability of directed cell migration toward to stiffer ECM fiber network as a function of separation distance. Three scatter plots in polar coordinates of r and θ represent distributions of time-averaged CPS at the filopodia (r) and time-averaged PA of the cell (θ). Note that PAs of 0°, 90°, and −90° indicate initial direction of cellular polarity and directions of stiff and soft ECM, respectively. (D–F) Variations of (D) time-averaged cellular PA, (E) traction force, and (F) CPS at the filopodial tip under three different separation distances of 10 µm, 20 µm, and 30 µm. All error bars in graphs indicate SE of mean.