Continuous and discontinuous dynamic unbinding transitions in drawn film flow

Area of Science:

• Fluid Dynamics
• Surface Science
• Non-equilibrium Physics

Background:

• Coating deposition on a withdrawing plate depends on withdrawal velocity and surface wettability.
• Understanding these dynamic processes is crucial for applications in material science and manufacturing.
• Existing models often focus on equilibrium states, neglecting dynamic transition behaviors.

Purpose of the Study:

• To investigate the dynamic transitions in coating thickness and homogeneity during plate withdrawal from a liquid bath.
• To incorporate wettability effects using Derjaguin pressure into a hydrodynamic model.
• To identify and characterize novel out-of-equilibrium dynamic transitions.

Main Methods:

• Employed a long-wave mesoscopic hydrodynamic description.
• Incorporated wettability through the Derjaguin (disjoining) pressure term.
• Analyzed the resulting equations to identify distinct dynamic regimes.

Main Results:

• Identified four distinct dynamic transitions between microscopic and macroscopic coating states.
• These transitions are continuous and discontinuous dynamic wetting and emptying phenomena.
• Observed unique features in these dynamic transitions that have no equilibrium counterparts.

Conclusions:

• The study reveals novel dynamic transitions in fluid coating processes.
• These out-of-equilibrium transitions expand our understanding beyond equilibrium wetting phenomena.
• Findings provide a more comprehensive model for dynamic coating behavior.