Colloidal systems find important applications ranging from fabrication ofphotonic crystals to direct probing of phenomena typically encountered inatomic crystals and glasses. New applications - such as nanoantennas, plasmonicsensors, and nanocircuits - pose a challenge of achieving sparse colloidalassemblies with tunable interparticle separations that can be controlled atwill. We demonstrate reconfigurable multiscale interactions and assembly ofcolloids mediated by defects in cholesteric liquid crystals that are probed bymeans of laser manipulation and three-dimensional imaging. We find thatcolloids attract via distance-independent elastic interactions when pinned tothe ends of cholesteric oily streaks, line defects at which one or more layersare interrupted. However, dislocations and oily streaks can also be opticallymanipulated to induce kinks, allowing one to lock them into the desiredconfigurations that are stabilized by elastic energy barriers for structuraltransformation of the particle-connecting defects. Under the influence ofelastic energy landscape due to these defects, sublamellar-sized colloidsself-assemble into structures mimicking the cores of dislocations and oilystreaks. Interactions between these defect embedded colloids can be varied fromattractive to repulsive by optically introducing dislocation kinks. Thereconfigurable nature of defect-particle interactions allows for patterning ofdefects by manipulation of colloids and, in turn, patterning of particles bythese defects, thus achieving desired colloidal configurations on scalesranging from the size of defect core to the sample size. This defect-colloidalsculpturing may be extended to other lamellar media, providing the means foroptically guided self-assembly of mesoscopic composites with predesignedproperties.
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