Figure 4.

(a) Leading, middle, and trailing regions along cell major axis. Traction force is analyzed by adding all force vectors in each of three regions. Angles θ indicates directions of traction force in each region by comparing resultant traction force with migration direction. Cell contour is indicated by yellow dashed line. Traction force is indicated by white arrows. Cell migration direction is labelled using blue arrow. (b) Force direction θ relative to migration direction in leading, middle, and trailing regions with total 41 cells analyzed. (c) Normalized cell traction force and speed as function of time for MC3T3 cell underwent forward migration on micropost arrays without guiding pattern. Arrows indicate moments when trailing region was released, starting at 75 and 117 min.