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Mechanics of disclination emergence in three-dimensional active nematics

Yingyou Ma, Christopher Amey, Aparna Baskaran*, and Michael F. Hagan†

  • *Contact author: aparna@brandeis.edu
  • †Contact author: hagan@brandeis.edu
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Phys. Rev. Research 8, 023019 – Published 7 April, 2026

DOI: https://doi.org/10.1103/lrrr-8h6x

Abstract

Active nematics have served as model systems for studying defect dynamics for decades, yet the general mechanism of defect formation in three dimensions (3D) remains unclear. Here, we introduce the principal-plane framework to study disclination-loop nucleation in 3D active nematics. This approach intuitively captures the 3D director field around disclinations and connects perturbative instability analysis with geometric characterization. With particle-based simulations, we further reveal that disclinations arise from the bend instability, while their tilt reflects the competition between activity and elasticity. We show that an activity-dependent effective stiffness κeff=κ/(1+2fa2) governs both defect morphology and the system's steady behavior. Together, these results establish a unified picture of disclination-loop emergence and provide design principles for controlling defect-driven dynamics in orientational materials.

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Phys. Rev. Research 8, 023019– Published 7 April, 2026
  • Received 1 July 2025
  • Accepted 20 February 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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