Dispersion of activity at an active-passive nematic interface

Abstract

Efficient nutrient mixing is crucial for the survival of bacterial colonies and other living systems. This raises the question of whether the optimization of mixing through the emergence of active turbulent motion in bacterial swarms played a role in the evolution of bacterial shapes. Here, to address this question, we solve the hydrodynamic equation for active nematics coupled with an advection-diffusion equation for the nutrients. The latter models a conserved activity field and mimics the conservation of nutrients in bacterial swarms. At the interface between active and passive nematic phases, in addition to diffusion, the activity is transported by interfacial flows and in turn modifies them through active stresses. We find that the interfacial dispersion of the conserved activity is subdiffusive due to the emergence of a barrier of negative defects at the active-passive interface, which hinders the propagation of the motile positive defects. Furthermore, we observe a non-monotonic dependence of the generalized diffusion coefficient on the aligning parameter, which is related to the shape of the particles. Our simulations suggest that there is an optimal shape that maximizes the dispersion of conserved activity at the active-passive nematic interface.

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Cited by in corpus (8)

• Active phase separation: new phenomenology from non-equilibrium physics
• Activity-suppressed phase separation
• Lattice Boltzmann simulation of deformable fluid-filled bodies: progress and perspectives
• Active nematics on flat surfaces: from droplet motility and scission to active wetting
• Active nematic pumps
• Phase Separation in Mixtures of Nematic and Isotropic Fluids
• Turbulence to order transitions in activity patterned active nematics
• Solute dispersion in pre-turbulent confined active nematics