Figure 3. Final orientation angle is correctly captured by the proposed theory.

As predicted by the theory (Eq. 7), a linear relation between cos²($\stackrel{‒}{\theta }$) and (r+1)⁻¹ is clearly observed, where $\stackrel{‒}{\theta }$ is the measured final orientation angle (blue circles are data from Fig. 2c). This excellent agreement (solid black line is the best fit to Eq. 7) depends on a single parameter, b, where both the slope and the intercept are uniquely determined by it (b =1.13 ± 0.04 extracted from fit). In comparison, the zero strain prediction (Eq. 1) is depicted by the dashed black line. Additional measurements - performed on a much softer substrate (~20 kPa compared to ~1MPa) (red squares) as well as data extracted from the literature for a different cell line ¹⁴ (green diamonds) – fall on the same line. This suggests that the elastic properties, associated with the b parameter in our theory, do not depend on substrate stiffness and are possibly cell line independent. Inset shows the same data, best fit and zero strain prediction, as above, with $\stackrel{‒}{\theta }$ plotted directly vs. r. Error bars represent 95% confidence intervals.