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Driven nematic colloids : From anomalous diffusion to dynamic self-assembly
Colloids dispersed in nematic liquid crystals are conventionally studied in equilibrium, where elastic interactions coming from the distortion of the nematic matrix are dominant. Here we consider driven nematic colloids both from individual and collective perspectives. Driving mechanism is mostly based on a nonlinear electrophoretic mechanism, which has a tensorial nature and, thus, can be guided at will relative to the far field orientation of the nematics.
For particular anchoring conditions at the colloid/nematic interface we find super-diffusive behavior for the individual colloidal motion transversal to the driving direction. The anomalous exponent is found to largely depend on particle size and temperature. Some theoretical hints will be given to interpret experimental results.
Collective behavior is manifested by large dynamic assemblies organized around topological defects of the nematic environment. These clusters show distinctive inhomogeneous properties at the level of the radial distribution of the number density. Results are interpreted in terms of a model that encompasses different levels of particle interactions, beyond conventionally elastic, of very different origin and length scales.