Universality of active wetting transitions

TL;DR

This study demonstrates that diverse active matter models exhibit universal wetting transitions at walls, with three phases and consistent critical exponents, revealing fundamental non-equilibrium behavior.

Contribution

It shows that different active matter models share universal wetting transition behavior and critical exponents, despite differences in microscopic dynamics.

Findings

Three distinct wetting phases identified: total wetting, partial wetting, dewetted.

Two continuous non-equilibrium phase transitions with universal critical exponents.

Critical exponents are consistent across all studied models.

Abstract

Four on-lattice and six off-lattice models for active matter are studied numerically, showing that in contact with a wall, they display universal wetting transitions between three distinctive phases. The particles, which interact via exclusion volume only, move persistently and, depending on the model, change their direction either via tumble processes or rotational diffusion. When increasing the turning rate $\nu_T$, the systems transit from total wetting, to partial wetting and dewetted phases. In the first phase, a wetting film covers the wall, with increasing heights while decreasing $\nu_T$. The second phase is characterized by wetting droplets on the walls. And, finally, the walls dries with few particles in contact with it. These phases present two continuous non-equilibrium transitions. For the first transition, from partial to total wetting, the fraction of dry sites vanishes continuously when decreasing $\nu_T$, with a power law of exponent 1. And, for the second transition, an order parameter proportional to the excess mass in droplets decreases continuously with a power law of exponent 3 when approaching a critical value of $\nu_T$. The critical exponents are the same for all the models studied.