Pattern Formation and Defect Ordering in Active Chiral Nematics.

Phys Rev Lett

Institute of Biomechanics and Medical Engineering, Applied Mechanics Laboratory, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China.

Published: August 2020

AI Article Synopsis

  • The study explores how individual spins in chiral rod-shaped aggregations lead to collective movement patterns, specifically vortex arrays with chirality.
  • It describes how stationary defects self-organize into a hexagon-dominated network, creating a consistent structure while displaying local symmetry breakdown.
  • The findings enhance our understanding of chiral patterns in biological systems and offer insights for manipulating self-organization in active materials.

Article Abstract

Many biological systems display intriguing chiral patterns and dynamics. Here, we present an active nematic theory accounting for individual spin to explore the collective handedness in chiral rod-shaped aggregations. We show that coordinated individual spin and motility can engender a vortex-array pattern with chirality and drive ordering of topological defects. During this chiral process, the stationary trefoil-like defects self-organize into a periodic, hexagon-dominated polygonal network, which segregates persistently rotating cometlike defects in pairs within each polygon, leading to a translation symmetry at the global scale while a broken reflection symmetry at the local scale. Such defect ordering agrees exactly with the Voronoi tiling of two-dimensional space and the emergence of the hexagonal symmetry is deciphered in analogy with topological charge neutralization. We calculate energy barriers to the topological transition of the defect ordering and explain the existing metastable states with nonhexagonal polygons. Our findings shed light on the chiral morphodynamics in life processes and also suggest a potential route towards tuning self-organization in active materials.

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Source
http://dx.doi.org/10.1103/PhysRevLett.125.098002DOI Listing

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