Spontaneous Ratchet Currents and Transition Dynamics in Active Wetting

TL;DR

This paper investigates active wetting phenomena in active matter, revealing a critical transition between wet states and discovering a spontaneous ratchet current that influences the transition dynamics, linking nonequilibrium activity to wetting behavior.

Contribution

It introduces an exact hydrodynamic model showing wetting transitions and spontaneous ratchet currents in active matter, highlighting nonequilibrium effects on wetting dynamics.

Findings

Existence of fully- and partially-wet states with a critical transition.

Discovery of a spontaneous-symmetry-breaking ratchet current.

Identification of a new dynamical pathway for wetting transition.

Abstract

Self-propelled particles accumulate on repulsive barriers in so-called active wetting, but the relationship between this process and equilibrium wetting remains unclear. Using an exact (noiseless) hydrodynamic framework for an active lattice gas, we show, using a slit geometry with periodic boundary conditions, that active matter exhibits both fully- and partially-wet states, with a critical wetting transition between them. Furthermore, we demonstrate the existence of a spontaneous-symmetry-breaking ratchet current in the partially wet state, leading to departure of the bulk densities from their binodal values and the emergence of a novel dynamical pathway for the full-to-partial wetting transition. We elucidate this modified dynamical pathway using a minimal model. The results, while establishing a direct connection between active and equilibrium wetting, also identify the nonequilibrium consequences of activity.