= Solution
Surface-treated colloids impose boundary conditions on a <nematic liquid crystal>, producing director distortions and defects. Bringing particles together can reduce total <Frank elastic energy> by sharing distortion or defect structures. The interactions are directional: particle–hedgehog dipoles can favor chains, while quadrupolar and confined configurations can favor other arrays. \b[The defects provide orientation-selective bonds rather than an isotropic attraction alone.]
Prepare a cell with controlled far-field alignment and particle anchoring. Image textures with a <polarizing microscope>; use optical tweezers to place two particles at selected separations and orientations, then release them and track their trajectories. Repeating over orientations tests anisotropy before increasing concentration to assemble larger arrays. Compare particles with different anchoring and compare with the isotropic phase to distinguish director-mediated binding from ordinary aggregation. Temperature-dependent viscosity and other surface forces must be accounted for in kinetic comparisons.
The reported two-dimensional nematic colloidal crystals used micrometre confinement and defect-mediated interactions to create ordered particle structures. This motivates the mechanism without implying that arbitrary particles will select the same lattice.<Two-Dimensional Nematic Colloidal Crystals Self-Assembled by Topological Defects by Igor Muševič and others>[2006, pp. 954–958, confined colloidal assembly and defect-mediated binding]{ref}
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