Lassoing Saddle-Splay: Topological Control of Topological Defects
Year: 2016
Type: preprint
Abstract: Systems with holes, such as colloidal handlebodies and toroidal droplets, have been studied in the nematic liquid crystal (NLC) 4-cyano-4'-pentylbiphenyl (5CB): both point and ring topological defects can occur within each hole and around the system and the overall topological charge of the system is conserved. However, what has not been fully appreciated is the ability of the hole geometry with homeotropic (perpendicular) anchoring conditions to back-react on the bulk and induce complex saddle-like deformations. We exploit this by creating an array of many holes suspended in an NLC cell with oriented planar (parallel) anchoring at the cell boundaries. We study both 5CB and a binary mixture of bicyclohexane derivatives (CCN-47 and CCN-55). Through simulations and experiments, we study how the bulk saddle deformations of each hole interact to create novel defect structures, including an array of disclination lines, reminiscent of those that occur in liquid crystal blue phases. The locations of these disclination lines are tunable via the elastic constants of the NLC, the geometry of the cell, and the size of the hole array. This research lays the groundwork for complex networks of elastic deformations of greatly varying length scales from simple geometrical cues in materials that are renowned in the display industry for their stability and easy manipulability, widening the potential for more intricate and controlled three-dimensional, self-assembled structures.
Source: arXiv (Cornell University)
Language: English
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2288043301