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Spontaneous Ratchet Currents and Transition Dynamics in Active Wetting.
Noah Grodzinski1, Robert L Jack1,2, Michael E Cates1
1Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge, United Kingdom.
Physical Review Letters
|July 10, 2026
Summary
Active wetting, where self-propelled particles meet barriers, shows both fully and partially wet states with a critical transition. A novel ratchet current emerges in the partially wet state, linking active and equilibrium wetting phenomena.
Area of Science:
- Physics
- Soft Matter Physics
- Statistical Mechanics
Background:
- Active wetting, involving self-propelled particles at interfaces, lacks clear links to equilibrium wetting.
- Understanding active matter behavior near repulsive barriers is crucial for soft matter physics.
Purpose of the Study:
- To investigate the relationship between active wetting and equilibrium wetting.
- To explore the phase behavior and emergent phenomena in active matter systems at repulsive barriers.
Main Methods:
- Utilized an exact, noiseless hydrodynamic framework for an active lattice gas model.
- Simulations were performed in a slit geometry with periodic boundary conditions.
Main Results:
- Identified both fully wet and partially wet states in the active matter system.
- Observed a critical wetting transition between these states.
- Demonstrated a spontaneous-symmetry-breaking ratchet current in the partially wet state, altering bulk densities.
Conclusions:
- Established a direct connection between active wetting and equilibrium wetting phenomena.
- Highlighted novel nonequilibrium consequences of particle activity, including a unique dynamical pathway for wetting transitions.
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