Topology of Orientational Defects in Confined Smectic Liquid Crystals

Monderkamp, Paul A.; Wittmann, René; Cortes, Louis; Aarts, Dirk G. A. L.; Smallenburg, Frank; Löwen, Hartmut

doi:10.1103/physrevlett.127.198001

“…91 The Euler characteristic w is an algebraic invariant. Accordingly, results of previous work agree for nematic 59 as well as smectic liquid crystals 80 confined to simply-connected convex cavities and for smectics confined to 2d spherical surfaces embedded in 3d. 60 In this work, we have presented examples for 3d simply-connected convex confinements, where the sum of topological charges defined through integrating around a closed contour in a 2d cross section matches the Euler characteristic w = 1 of this cross section.…”

Section: Topological Chargesupporting

confidence: 85%

“…This bridge state can generally be observed for a large range of confinements. 80 Indeed, we find that this reference structure also persists when extending the system into the third dimension.…”

Section: Detection Of Defects Via Order Parametersmentioning

confidence: 60%

Topological fine structure of smectic grain boundaries and tetratic disclination lines within three-dimensional smectic liquid crystals

Monderkamp

¹

,

Wittmann

²

,

Vrugt

³

et al. 2022

Phys. Chem. Chem. Phys.

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“…[7]); interpolating between that limit and the one studied here parametrizes a family of possible active nematic models. Additionally, the view of our system as a nematic fluid ignores orientational discontinuities along linear grain boundaries, which have been shown to play in important role in confined, two-dimensional smectic liquid crystals of hard rods [56]. Applying this perspective and including grain boundaries into analysis of particle-based active nematics simulations might give new insights into the structure and growth of bacterial colonies.…”

Section: Discussionmentioning

confidence: 99%

Do Active Nematic Self-Mixing Dynamics Help Growing Bacterial Colonies to Maintain Local Genetic Diversity?

Schwarzendahl

¹

,

Beller

²

2022

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Recent studies have shown that packings of cells, both eukaryotic cellular tissues and growing or swarming bacterial colonies, can often be understood as active nematic fluids. A key property of volume-conserving active nematic model systems is chaotic self-mixing characterized by motile topological defects. However, for active nematics driven by growth rather than motility, less is understood about mixing and defect motion. Mixing could affect evolutionary outcomes in bacterial colonies by counteracting the tendency to spatially segregate into monoclonal sectors, which reduces the local genetic diversity and confines competition between subpopulations to the boundaries between neighboring sectors. To examine whether growth-driven active nematic physics could influence this genetic demixing process, we conduct agent-based simulations of growing, dividing, and sterically repelling rod-like bacteria of various aspect ratios, and we analyze colony morphology using tools from both soft matter physics and population genetics. We find that despite measurable defect self-propulsion in growth-driven active nematics, the radial expansion flow prevents chaotic mixing. Even so, at biologically relevant cell aspect ratios, self-mixing is more effective in growing active nematics of rod-like cells compared to growing isotropic colonies of round cells. This suggests potential evolutionary consequences associated with active nematic dynamics.

show abstract

“…[6]). Additionally, the view of our system as a nematic fluid ignores orientational discontinuities along linear grain boundaries, which have been shown to play in important role in confined, two-dimensional smectic liquid crystals of hard rods [52]. Applying this perspective and including grain boundaries into analysis of particle-based active nematics simulations might give new insights into the structure and growth of bacterial colonies.…”

Section: Discussionmentioning

confidence: 99%

Do active nematic self-mixing dynamics help growing bacterial colonies to maintain local genetic diversity?

Schwarzendahl¹,

Beller²

2022

Preprint

View full text Add to dashboard Cite

Recent studies have shown that packings of cells, both eukaryotic cellular tissues and growing or swarming bacterial colonies, can often be understood as active nematic fluids. A key property of volume-conserving active nematic model systems is chaotic self-mixing characterized by motile topological defects. However, for active nematics driven by growth rather than motility, less is understood about mixing and defect motion. Mixing could affect evolutionary outcomes in bacterial colonies by counteracting the tendency to spatially segregate into monoclonal sectors, which reduces the local genetic diversity and confines competition between subpopulations to the boundaries between neighboring sectors. To examine whether growth-driven active nematic physics could influence this genetic demixing process, we conduct agent-based simulations of growing, dividing, and sterically repelling rod-like bacteria of various aspect ratios, and we analyze colony morphology using tools from both soft matter physics and population genetics. We find that despite measurable defect self-propulsion in growth-driven active nematics, the radial expansion flow prevents chaotic mixing. Even so, at biologically relevant cell aspect ratios, self-mixing is more effective in growing active nematics of rod-like cells compared to growing isotropic colonies of round cells. This suggests potential evolutionary consequences associated with active nematic dynamics.

show abstract

Topology of Orientational Defects in Confined Smectic Liquid Crystals

Cited by 29 publications

References 109 publications

Topological fine structure of smectic grain boundaries and tetratic disclination lines within three-dimensional smectic liquid crystals

Topological fine structure of smectic grain boundaries and tetratic disclination lines within three-dimensional smectic liquid crystals

Do Active Nematic Self-Mixing Dynamics Help Growing Bacterial Colonies to Maintain Local Genetic Diversity?

Do active nematic self-mixing dynamics help growing bacterial colonies to maintain local genetic diversity?

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