The effect of self-induced Marangoni flow on polar-nematic waves in active-matter systems

Abstract

We study the formation of propagating large-scale density waves of mixed polar-nematic symmetry in a colony of self-propelled agents that are bound to move along the planar surface of a thin viscous film. The agents act as an insoluble surfactant, i.e. the surface tension of the liquid depends on their density. Therefore, density gradients generate a Marangoni flow. We demonstrate that for active matter in the form of self-propelled surfactants with local (nematic) aligning interactions such a Marangoni flow nontrivially influences the propagation of the density waves. Upon gradually increasing the Marangoni parameter, which characterises the relative strength of the Marangoni flow as compared to the self-propulsion speed, the density waves broaden while their speed may either increase or decrease depending on wavelength and overall mean density. A further increase of the Marangoni parameter eventually results in the disappearance of the density waves. This may occur either discontinuously at finite wave amplitude via a saddle-node bifurcation or continuously with vanishing wave amplitude at a wave bifurcation, i.e. a finite-wavelength Hopf bifurcation.

References in corpus (13)

• Novel type of phase transition in a system of self-driven particles
• Fluctuation-Dissipation: Response Theory in Statistical Physics
• Hydrodynamic equations for self-propelled particles: microscopic derivation and stability analysis
• Colloidal motility and pattern formation under rectified diffusiophoresis
• Light Activated Self-Propelled Colloids
• Motility-induced phase separation and coarsening in active matter
• Long-wave theory of bounded two-layer films with a free liquid-liquid interface: Short- and long-time evolution
• Suppression of coarsening and emergence of oscillatory behavior in a Cahn-Hilliard model with nonvariational coupling
• Nonreciprocal Cahn-Hilliard model emerges as a universal amplitude equation
• Thermodynamically consistent description of the hydrodynamics of free surfaces covered by insoluble surfactants of high concentration
• Stability of liquid films covered by a carpet of self-propelled surfactant particles
• Dynamics of microswimmers near a liquid-liquid interface with viscosity difference
• An amplitude equation for the conserved-Hopf bifurcation -- derivation, analysis and assessment