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Magnetic-field-driven director configuration transitions in radial nematic liquid crystal droplets.

Magnetic-field-driven director configuration transitions in radial nematic liquid crystal droplets.

Authors :
Ettinger S
Slaughter CG
Parra SH
Kikkawa JM
Collings PJ
Yodh AG
Source :
Physical review. E [Phys Rev E] 2023 Aug; Vol. 108 (2-1), pp. 024704.
Publication Year :
2023

Abstract

We study the director configurations of nematic liquid crystal (NLC) droplets with homeotropic anchoring in a magnetic field and report observation of a magnetic-field-driven transition from a deformed radial to an axial-with-defect configuration. Magnetic-field-induced transitions in NLC droplets differ fundamentally from the traditional planar Freedericksz transition due to the spherical droplet geometry and resulting topological defect. This transition has been studied theoretically, but the director configurations and mechanism of defect evolution in an applied magnetic field have yet to be observed experimentally. To this end, we combine polarized optical microscopy with a variable electromagnet (≤1 T) for continuous observation of droplet director fields, and we employ Landau-de Gennes numerical simulations to elucidate the director configurations and first-order nature of the transition. We report a configuration transition from point defect to ring defect at a critical field, which varies inversely with droplet radius and is relatively independent of surfactant type and concentration. We also estimate anchoring strengths of commonly used surfactants at the NLC-aqueous interface.

Details

Language :
English
ISSN :
2470-0053
Volume :
108
Issue :
2-1
Database :
MEDLINE
Journal :
Physical review. E
Publication Type :
Academic Journal
Accession number :
37723717
Full Text :
https://doi.org/10.1103/PhysRevE.108.024704