\[\begin{equation} \begin{array}{cc} \phi\approx\tan^{-1}\left\{\frac{\sum_{k=1}^N\cos\alpha_{2k-1}+\cos_{2k}}{\sum_{k=1}^N\sin\alpha_{2k-1}+\sin\alpha_{2k}}\right\}\\ \\ =\tan^{-1}\left\{\frac{\sum_{k=1}^N\sin\left\{\left(2k-1\right)\left(\theta_{free}-\theta_{ori}\right)\right\}}{\sum_{k=1}^N\cos\left\{\left(2k-1\right)\left(\theta_{free}-\theta_{ori}\right)\right\}}\right\}\\ \\ =N\left(\theta_{free}-\theta_{ori}\right)\\ \end{array} \end{equation} \]
In Figure.S2C, the model was compared with the experimental result, and it was well suited for low applied pressure.
 
Change in effective layer length \(\Delta L\) can be approximated as a length of an arc: