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Colloidal crystals in curved space: Pleating and fractionalization by topological defects

Event Details

Event Dates: 

Tuesday, February 5, 2013 - 5:00am

Speaker Name(s): 

William Irvine

Speaker Affiliation(s): 

University of Chicago
Seminar Type/Subject

Event Details & Abstract: 

Colloidal crystals in curved space: Pleating and fractionalization by topological defects Geometric constraints can play a key role in directing the self-assembly of soft matter.  Repulsive particles confined to a flat surface spontaneously organize into perfect hexagonal crystals. If confined instead to the surface of a sphere, defects must appear in the form of pentagonal disclinations that carry positive topological charge.  On spheres large compared to the lattice spacing, the disclinations become dressed by dislocations (topological dipoles) to form `scars'.  We create colloidal crystals on capillary bridges having positive, negative and varying Gaussian curvature as well as boundaries. We  observe the direct interaction of isolated dislocations with curvature and the spontaneous organization of groups of dislocations into topologically neutral structures akin to fabric pleats. Using a setup that combines holographic optical tweezing with confocal imaging, we add particles to the curved crystal and witness a curvature-driven self-healing mechanism that results from the decay of interstitials into unbound defect pairs.