Capillary action in scalar active matter

Abstract

We study the capacity of active matter to rise in thin tubes against gravity and other related phenomena, like, wetting of vertical plates and spontaneous imbibition, where a wetting liquid is drawn into a porous medium. This capillary action or capillarity is well known in classical fluids and originates from attractive interactions between the liquid molecules and the container walls, and from the attraction of the liquid molecules among each other. We observe capillarity in a minimal model for scalar active matter with purely repulsive interactions, where an effective attraction emerges due to slowdown during collisions between active particles and between active particles and walls. Simulations indicate that the capillary rise in thin tubes is approximately proportional to the active sedimentation length $\lambda$ and that the wetting height of a vertical plate grows superlinear with $\lambda$. In a disordered porous medium the imbibition height scales as $⟨h⟩\propto \lambda {\varphi }_m$, where ${\varphi }_m$ is its packing fraction.

6 pages, 5 figures

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Cited by in corpus (10)

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• Active particles with polar alignment in ring-shaped confinement
• Stationary particle currents in sedimenting active matter wetting a wall
• Interfacial and density fluctuations in a lattice model of motility-induced phase separation
• Active Young-Dupré Equation: How Self-organized Currents Stabilize Partial Wetting
• Ordering kinetics in the active Ising model
• What is active wetting?
• An Infinite Set of Integral Formulae for Polar, Nematic, and Higher Order Structures at the Interface of Motility-Induced Phase Separation