Nematic Textures in Spherical Shells

These shells with nematic order can exhibit completely new defect structure. Defects are inherent in liquid crystals, where the nematic order of the liquid crystal requires that defects be induced in the sample when placed in any real-world environment. A very thin shell has 4-fold defect structure, as illustrated by the baseball in the upper left. However, when the thickness of the shell increases, one pair of defects can "escape" into the inside of the shell, leaving only two defects on the top, as illustrated in the lower left. Shells made from nematic liquid crystal exhibit exactly the same thing, as shown by the examples on the right which are viewed through crossed polarizers. A very thin shell has four defects (top) while a thicker shell has only two (bottom).

Harvard MRSEC (DMR-0820484)