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Nematic colloids entangled by topological defects

SoftMatter_cover.jpgColloids in complex fluids is a current hot topic at Ljubljana university and in soft matter physics in general. The cover of a recent issue of the Soft Matter journal features Nematic colloids entangled by topological defects, a paper published by Miha Ravnik and Slobodan ┼Żumer.

Assembly of colloidal particles in nematic liquid crystals is governed by the symmetry of building blocks and type of defects in the liquid crystalline orientation. Particles in a nematic act as nucleation sites for topological defect structures that are homotopic to point defects. The tendency for a minimal deformation free energy and topological constraints limit possible defect configurations to extended and localized defect loops. We report on a recently discovered colloidal binding, where particles are entangled by disclination loops. Nematic braids formed by such disclinations stabilize multi-particle objects and entrap particles in a complex manner. Observed binding potentials are highly anisotropic showing string-like behavior.