Two-Dimensional Nematic Colloidal Crystals Self-Assembled by Topological Defects

When colloidal particles are confined to a few micrometer-thick layer of a nematic liquid crystal form two-dimensional crystal structures that are bound by topological defects. Two basic crystalline structures were observed, depending on the ordering of the liquid crystal around the particle. Colloidal particles inducing quadrupolar order crystallize into weakly bound two-dimensional ordered structure, where the particle interaction is mediated by the sharing of localized topological defects. Colloids inducing dipolar order are strongly bound into antiferroelectric-like two-dimensional crystallites of dipolar colloidal chains.

Dipolar colloids in nematic liquid crystal spontaneously form dipolar chains along the rubbing direction.	Self asembeled clusters of dipoles.	2D dipolar colloidal crystal formed by pairs of antiparallel dipolar chains.
Quadrupolar colloids spontaneously formkinked chains perpendicular to the direction of rubbing.	Self asembeled clusters of quadrupoles.	Large quadrupolar crystal formed by directed laser tweezers assembly of colloidal particles.

MUŠEVIČ, Igor, ŠKARABOT, Miha, TKALEC, Uroš, RAVNIK, Miha, ŽUMER, Slobodan. Two-dimensional nematic colloidal crystals self-assembled by topological defects. Science 313, 954-958 (2006).