Spontaneous surface roughening induced by surface interactions between two compressible elastic films

Area of Science:

• Physics
• Materials Science
• Surface Science

Background:

• Soft elastic films bonded to rigid substrates can exhibit spontaneous surface roughening.
• This phenomenon is driven by attractive intersurface interactions when the distance between surfaces becomes critical.
• Compressibility of the films significantly influences the conditions and characteristics of this roughening instability.

Purpose of the Study:

• To investigate the effects of material compressibility on the onset and length scale of surface roughening in elastic films.
• To determine the critical force and wavelength of instability as functions of compressibility.
• To analyze the influence of film compliance on the resulting surface morphology.

Main Methods:

• Theoretical analysis of elastic film mechanics.
• Modeling of intersurface interactions and instability criteria.
• Parametric study varying compressibility (Poisson's ratio, nu) and film properties.

Main Results:

• Surface roughening is suppressed for highly compressible films (nu < 0.25).
• Increased compressibility reduces the critical force for instability and alters the wave number.
• The wavelength of the surface instability is predominantly governed by the more compliant film's properties.

Conclusions:

• Compressibility is a critical factor controlling spontaneous surface roughening in elastic films.
• The transition to roughening and the resulting instability wavelength are sensitive to the balance of film compliances.
• Understanding these effects is crucial for designing and fabricating thin-film devices where surface morphology is important.