Fig. 6.

Cross-section profiles of the strips inspected. The orange color of the strips indicate prestretching state; blue strips are stress-free in the initial state. As indicated by the ticks and crosses at the lower-right corner of each figure, A–C can produce helices and perversions, whereas D and E only deform to V-like shape. The geometric parameters of the strips are $w_0=9\hspace{0.5em}\text{mm}$, w is the width after prestretching, and $w\prime$ can vary from $5.4\sim 6.3\hspace{0.5em}\text{mm}$, $h=3\hspace{0.5em}\text{mm}$, and $h\prime =0.2\hspace{0.5em}\text{mm}$.