Fig. 2.

Cholesteric shells with bivalent defect structure. (A) Schematics showing the geometry of experimental shells. (B) Top view of a bivalent experimental cholesteric shell showing its two outer surface defects. (Inset) Sketch of the director field around those defects. (C) Planar and escaped structures of +1 disclinations in nematics. (D) ${\chi }^{+1}$-, ${\lambda }^{+1/2}$-, and ${\tau }^{-1/2}$-disclinations in cholesterics. The nails represent an out-of-plane director field, where the nail heads indicate the extremity pointing upwardly. (E) Simulated cholesteric droplet with diametrical spherical structure (DSS). Reproduced from ref. 14. (F) Tilted view of a bivalent experimental cholesteric shell, where the position of the defects is indicated by arrows and the inner structure of one of the two defects is zoomed in on. (G) Simulated cholesteric shell with DSS. (H) Number of disclination rings as a function of $\lfloor 2h/p\rfloor$ in a DSS structure, from numerical predictions (blue) and observations (red). B and F are cross-polarized images. (Scale bar, $20\hspace{0.17em}\mu \text{m}$.)