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Malleability of metals is an example of how the dynamics of defects like dislocations induced by external stresses alters material properties and enables technological applications. However, these defects move merely to comply with the mechanical forces applied on macroscopic scales, whereas the molecular and atomic building blocks behave like rigid particles. Here, we demonstrate how motions of crystallites and the defects between them can arise within the soft matter medium in an oscillating electric field applied to a chiral liquid crystal with polycrystalline quasi-hexagonal arrangements of self-assembled topological solitons called “torons.” Periodic oscillations of electric field applied perpendicular to the plane of hexagonal lattices prompt repetitive shear-like deformations of the solitons, which synchronize the electrically powered self-shearing directions. The temporal evolution of deformations upon turning voltage on and off is not invariant upon reversal of time, prompting lateral translations of the crystallites of torons within quasi-hexagonal periodically deformed lattices. We probe how these motions depend on voltage and frequency of oscillating field applied in an experimental geometry resembling that of liquid crystal displays. We study the interrelations between synchronized deformations of the soft solitonic particles and their arrays, and the ensuing dynamics and giant number fluctuations mediated by motions of crystallites, five–seven defects pairs, and grain boundaries in the orderly organizations of solitons. We discuss how our findings may lead to technological and fundamental science applications of dynamic self-assemblies of topologically protected but highly deformable particle-like solitons.
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Quasicrystalline Arrays and Moiré Patterns in Nematic Liquid Crystals for Soft Photonics
Abstract The search for new strategies for large‐scale, self‐assembled arrays of soft objects is key for many applications in photonics and bottom‐up manufacturing. This work shows how liquid crystal topological defects can be assembled in controlled, aperiodic arrays. In particular, the focus is on two typical examples: quasicrystals and moiré patterns. Thanks to a combination of topographical cues, specifically a micropillar array and electrical switching, defects can be assembled in a quasicrystal structure, as seen from polarized optical microscopy and from diffraction patterns. In this setting, the liquid crystal defects assemble in multiple patterns that can be switched by tuning the applied electric field and retain the quasicrystalline symmetry. Using topographic cues, it is also possible to induce moiré patterns of defects, characterized by a long wavelength superimposed on the periodic structures over a short scale. Even when the defect density increases and the short‐scale periodicity is lost, the long‐scale one remains. This work shows how versatile the combination of topographic confinement and electro‐optic effect is, giving access to patterns that are otherwise difficult to realize.
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- Award ID(s):
- 2004532
- PAR ID:
- 10371947
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Optical Materials
- Volume:
- 10
- Issue:
- 22
- ISSN:
- 2195-1071
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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