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Updated: Jun 23, 2025
08:37
Forming, Confining, and Observing Microtubule-Based Active Nematics
Published on: January 13, 2023
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Controlling Chaos: Periodic Defect Braiding in Active Nematics Confined to a Cardioid
Fereshteh L Memarian1, Derek Hammar1, Md Mainul Hasan Sabbir1
1Department of Physics, University of California, Merced, 5200 North Lake Road, Merced, California 95343, USA.
Physical Review Letters
|June 15, 2024
Summary
Confining active nematics in cardioid shapes creates a "golden braid," an efficient three-defect mixing state. Larger cardioids transition this state to chaotic turbulence.
Area of Science:
- Soft Matter Physics
- Fluid Dynamics
- Nonlinear Dynamics
Background:
- Active nematics are complex fluids with mobile topological defects.
- These defects drive chaotic flows, influencing material mixing.
- Understanding defect dynamics is key to controlling active matter systems.
Purpose of the Study:
- To investigate the effect of geometrical confinement on defect braiding in active nematics.
- To demonstrate the realization of the "golden braid" state under specific confinement conditions.
- To analyze the transition from ordered braiding to chaotic turbulence.
Main Methods:
- Experimental realization of active nematics using biological filaments and molecular motors.
- Utilizing cardioid-shaped microfluidic wells for geometrical confinement.
- Characterization using topological entropy measurements and Lyapunov exponent analysis.
Main Results:
- Confinement in cardioid wells promotes the "golden braid" state with three defects.
- This state exhibits maximally efficient mixing without defect creation or annihilation.
- Topological entropy measurements align with braid theory predictions.
- Increasing confinement size transitions the system from the golden braid to active turbulence.
Conclusions:
- Geometrical confinement is a powerful tool to control defect dynamics in active nematics.
- The "golden braid" represents a stable, highly efficient mixing state.
- Active nematics exhibit tunable transitions between ordered and chaotic states based on confinement geometry.
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