Colloid Particles in the Interaction Field of a Disclination Line in a Nematic Phase

Abstract

On the basis of linear hydrodynamics, we analyze the trajectory of particle-hedgehog systems, attracted by a -1/2 disclination (defect line) in a nematic liquid crystal. We show that, as with the interactions between like-particles, the interaction between a particle and a disclination has an electrostatic analogue, the splay replacing the electric field, except for the symmetry properties. The disclination thus attracts the beads along nonradial tracks and in a self-assembling process, or template mechanism, may build a microscopic necklace with them.

Transport of particles in liquid crystals

“…For example, the cores of line defects that frame focal conic domains in smectic LC can lift spherical particles above the base of the domain to minimize the surface anchoring energy 59 . Colloidal particles have been shown to be attracted by the cores of point defects 33 and disclination lines 58,104 . An example of accumulation of polymer particles at the core of a singular disclination of strength 1/2 is illustrated in Fig.…”

Nematic Liquid Crystals and Nematic Colloids in Microfluidic Environment

“…Such confinements, popularly known was LC cells, are frequently employed both in research and in applications. In fact, by an appropriate selection of the surface anchoring, topological defects can be created with sufficient control and reproducibility [134,180]. On the contrary, industrial applications rely on defect-free nematic samples.…”

“…Depending upon topological charge, either four or two dark brushes are observed between crossed polarizers. Disclination lines connecting the point defects of equal topological charge are generated spontaneously when the confining surfaces are brought in close proximity [134]. The nucleation and subsequent stabilization of such defect lines are additionally assisted by irregularities on the confining surfaces and by the presence of dispersed impurities.…”

“…However, both types of colloids, isolated particles as well as chains, can be transported on the soft rails. In the vicinity of a defect line, the colloids were captured by the line [134]. Following the elasticity-mediated trapping, the surrounding flow field moved the particles with the local flow velocity along the disclination track.…”

“…Indeed, it has been shown by Galerne and co-workers, that colloidal particles show anisotropic attractive or repulsive forces in the vicinity of a defect line. Please refer to [126,134] for futher details. …”