Active extensile stress promotes 3D director orientations and flows

Abstract

We use numerical simulations and linear stability analysis to study an active nematic layer where the director is allowed to point out of the plane. Our results highlight the difference between extensile and contractile systems. Contractile stress suppresses the flows perpendicular to the layer and favours in-plane orientations of the director. By contrast, extensile stress promotes instabilities that can turn the director out of the plane, leaving behind a population of distinct, in-plane regions that continually elongate and divide. This supports extensile forces as a mechanism for the initial stages of layer formation in living systems, and we show that a planar drop with extensile (contractile) activity grows into three dimensions (remains in two dimensions). The results also explain the propensity of disclination lines in three dimensional active nematics to be of twist-type in extensile or wedge-type in contractile materials.

References in corpus (5)

• Meso-scale turbulence in living fluids
• Active matter
• Steady-state hydrodynamic instabilities of active liquid crystals: Hybrid lattice Boltzmann simulations
• Spontaneous mirror-symmetry breaking induces inverse energy cascade in 3D active fluids
• Defect Spirograph: Dynamical Behavior of Defects in Spatially Patterned Active Nematics

Cited by in corpus (10)

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• Spontaneous rotation of active droplets in two and three dimensions
• Spontaneous flow instabilities of active polar fluids in three dimensions
• Two-temperature activity induces liquid-crystal phases inaccessible in equilibrium
• Active nematic pumps
• Microswimmers knead nematics into cholesterics
• Spontaneous flow created by active topological defects