Nonlinear instabilities and pathways of rupture in thin liquid bilayers

Area of Science:

• Fluid dynamics
• Surface science
• Materials science

Background:

• Dewetting of thin liquid films is crucial in various applications.
• Understanding bilayer dewetting dynamics is complex due to multiple interfaces.
• Van der Waals forces significantly influence interfacial behavior.

Purpose of the Study:

• To analyze the long-wave nonlinear dewetting of thin liquid bilayers (<100 nm) on solid substrates.
• To investigate the roles of interfacial energies, film thicknesses, and viscosities in dewetting pathways.
• To explore the evolution of interfacial morphologies and rupture mechanisms.

Main Methods:

• Long-wave nonlinear analysis.
• Linear stability analysis for predicting initial instability modes.
• Nonlinear simulations to verify predictions and explore late-stage dynamics.

Main Results:

• Identified two primary initial dewetting instability modes: in-phase bending and out-of-phase squeezing.
• Demonstrated that interfacial energies and film thicknesses determine the dominant initial mode.
• Showcased how intermolecular and viscous forces alter initial instabilities, leading to diverse late-stage morphologies such as embedded droplets and phase inversion.

Conclusions:

• Dewetting pathways in liquid bilayers are highly sensitive to initial conditions and intermolecular forces.
• Nonlinear effects are critical for understanding complex, late-stage dewetting patterns.
• Tuning interfacial and intermolecular forces offers control over dewetting outcomes.