Figure 4.

Correlation of cell proliferation rate constant k with substratum surface energy for hFOB. Surface energy is here measured by water adhesion tension ${\tau }^o={\gamma }_{lv}^{o}cos\theta$, where ${\gamma }_{lv}^o=72.8\text{dyne}/\text{cm}$ at 20° C for pure water and θ is the angle subtended by a water droplet on the surface understudy (advancing θ = filled symbols, receding θ = open symbols; adapted from ref. [60]). Error bars represent standard deviation of N ≥ 3. Trend-line through advancing and receding data is guide to the eye. Material identification is the same as in Fig. 3.