  Colloidal systems find important applications ranging from fabrication of
photonic crystals to direct probing of phenomena typically encountered in
atomic crystals and glasses. New applications - such as nanoantennas, plasmonic
sensors, and nanocircuits - pose a challenge of achieving sparse colloidal
assemblies with tunable interparticle separations that can be controlled at
will. We demonstrate reconfigurable multiscale interactions and assembly of
colloids mediated by defects in cholesteric liquid crystals that are probed by
means of laser manipulation and three-dimensional imaging. We find that
colloids attract via distance-independent elastic interactions when pinned to
the ends of cholesteric oily streaks, line defects at which one or more layers
are interrupted. However, dislocations and oily streaks can also be optically
manipulated to induce kinks, allowing one to lock them into the desired
configurations that are stabilized by elastic energy barriers for structural
transformation of the particle-connecting defects. Under the influence of
elastic energy landscape due to these defects, sublamellar-sized colloids
self-assemble into structures mimicking the cores of dislocations and oily
streaks. Interactions between these defect embedded colloids can be varied from
attractive to repulsive by optically introducing dislocation kinks. The
reconfigurable nature of defect-particle interactions allows for patterning of
defects by manipulation of colloids and, in turn, patterning of particles by
these defects, thus achieving desired colloidal configurations on scales
ranging from the size of defect core to the sample size. This defect-colloidal
sculpturing may be extended to other lamellar media, providing the means for
optically guided self-assembly of mesoscopic composites with predesigned
properties.
