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Stable nematic droplets with handles

Pairam, Ekapop, Vallamkondu, Jayalakshmi, Koning, Vinzenz, van Zuiden, Benjamin C., Ellis, Perry W., Bates, Martin A., Vitelli, Vincenzo, Fernandez-Nieves, Alberto
Proceedings of the National Academy of Sciences of the United States of America 2013 v.110 no.23 pp. 9295-9300
computer simulation, droplets, energy, liquid crystals, topology
We stabilize nematic droplets with handles against surface tension-driven instabilities, using a yield-stress material as outer fluid, and study the complex nematic textures and defect structures that result from the competition between topological constraints and the elasticity of the nematic liquid crystal. We uncover a surprisingly persistent twisted configuration of the nematic director inside the droplets when tangential anchoring is established at their boundaries, which we explain after considering the influence of saddle splay on the elastic free energy. For toroidal droplets, we find that the saddle-splay energy screens the twisting energy, resulting in a spontaneous breaking of mirror symmetry; the chiral twisted state persists for aspect ratios as large as ∼20. For droplets with additional handles, we observe in experiments and computer simulations that there are two additional −1 surface defects per handle; these are located in regions with local saddle geometry to minimize the nematic distortions and hence the corresponding elastic free energy.