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Area of Science:

  • Soft Matter Physics
  • Active Matter Systems
  • Fluid Dynamics

Background:

  • Active nematic systems exhibit complex behaviors driven by internal stresses.
  • Spatial variations in active stress can significantly alter system dynamics and defect behavior.
  • Understanding these responses is crucial for biological applications.

Purpose of the Study:

  • To numerically investigate the impact of spatial active stress variations on active nematic systems.
  • To characterize the resulting flows, director reorientation, and defect dynamics in 2D and 3D.
  • To determine defect alignment rules in response to activity gradients.

Main Methods:

  • Numerical simulations of active nematic systems in two and three dimensions.
  • Analysis of flow fields, director orientation, and defect structures.
  • Investigation of systems with and without defects under varying activity gradients.

Main Results:

  • Activity gradients induce flows that reorient the nematic director, acting as an anchoring force.
  • High activity leads to defect creation and a transition to active turbulence.
  • In 2D, +1/2 defects align parallel to gradients, pointing towards contractile regions.
  • In 3D, disclination lines lie perpendicular to gradients; defect structures show specific alignments based on type.

Conclusions:

  • Active stress gradients are key drivers of emergent behavior in active nematics.
  • Defect structures exhibit predictable alignments with activity gradients in both 2D and 3D.
  • Findings provide insights into morphogenetic processes and cell aggregate dynamics.