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Topological defects in active nematics drive large-scale organization. This study analytically reveals flow and stress patterns around these defects, explaining cellular behaviors like extrusion.

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Area of Science:

  • Soft Matter Physics
  • Active Matter Systems
  • Liquid Crystal Science

Background:

  • Topological defects are crucial for organizing liquid crystals, especially in 2D active nematics.
  • Active stresses associated with these defects significantly influence system behavior.
  • Analytical understanding of flow and stress fields around active topological defects remains limited.

Purpose of the Study:

  • To analytically investigate flow and active-stress patterns around topological defects in 2D active nematics.
  • To derive spontaneous velocity and stall force for self-advected defects.
  • To apply these findings to understand cell monolayer dynamics and phenomena like cellular extrusion.

Main Methods:

  • Utilizing the generic hydrodynamic theory of active systems.
  • Deriving analytical solutions for flow and stress fields under generic assumptions.
  • Incorporating shear and rotational viscosities.
  • Numerically investigating the influence of Ericksen stress.

Main Results:

  • Analytical expressions for spontaneous velocity and stall force of self-advected defects were derived.
  • Non-conservation of cell number was shown to generically increase self-advection velocity in cell monolayers.
  • The study provides a potential explanation for the role of topological defects in cellular extrusion and multilayering.

Conclusions:

  • The hydrodynamic theory provides a powerful framework for studying active topological defects.
  • Findings offer insights into the collective behavior of active matter, particularly cell monolayers.
  • This work lays the groundwork for broader investigations into topological defects in active nematics and biological systems.