Structures and topological defects in pressure-driven lyotropic chromonic liquid crystals

Lyotropic chromonic liquid crystals are water-based materials composed of self-assembled cylindrical aggregates. Their behavior under flow is poorly understood, and quantitatively resolving the optical retardance of the flowing liquid crystal has so far been limited by the imaging speed of current p...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2021-08, Vol.118 (35), p.1-9
Main Authors: Zhang, Qing, Zhang, Rui, Ge, Baoliang, Yaqoob, Zahid, So, Peter T. C., Bischofberger, Irmgard
Format: Article
Language:English
Subjects:
Anisotropy
Aspect ratio
Computer Simulation
Cromolyn Sodium - chemistry
Crystal defects
Crystal structure
Crystals
Dynamic structural analysis
Imaging
Imaging techniques
Liquid crystals
Liquid Crystals - chemistry
Microfluidic devices
Microfluidics
Models, Chemical
Nucleation
Phase Transition
Physical Sciences
Polarization
Pressure
Retardance
Self-assembly
Shearing
Spatial distribution
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Summary:Lyotropic chromonic liquid crystals are water-based materials composed of self-assembled cylindrical aggregates. Their behavior under flow is poorly understood, and quantitatively resolving the optical retardance of the flowing liquid crystal has so far been limited by the imaging speed of current polarization-resolved imaging techniques. Here, we employ a single-shot quantitative polarization imaging method, termed polarized shearing interference microscopy, to quantify the spatial distribution and the dynamics of the structures emerging in nematic disodium cromoglycate solutions in a microfluidic channel. We show that pure-twist disclination loops nucleate in the bulk flow over a range of shear rates. These loops are elongated in the flow direction and exhibit a constant aspect ratio that is governed by the nonnegligible splay-bend anisotropy at the loop boundary. The size of the loops is set by the balance between nucleation forces and annihilation forces acting on the disclination. The fluctuations of the pure-twist disclination loops reflect the tumbling character of nematic disodium cromoglycate. Our study, including experiment, simulation, and scaling analysis, provides a comprehensive understanding of the structure and dynamics of pressure-driven lyotropic chromonic liquid crystals and might open new routes for using these materials to control assembly and flow of biological systems or particles in microfluidic devices.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.2108361118