Nematic colloids entangled by topological defects

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. Here 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 and can be of an order of magnitude stronger compared to non-entangled colloids. Controlling the assembly based on entangled disclination lines one can build multi-particle structures with potentially useful features (shapes, periodic structure, chirality, etc.) for photonic and plasmonic applications.