Contact Instability in Adhesion and Debonding of Thin Elastic Films

TL;DR

This study investigates the morphological transitions of thin elastic films during adhesion and debonding, revealing a consistent pattern length scale influenced by film thickness, surface tension, and shear modulus through experiments, simulations, and stability analysis.

Contribution

It introduces a new thin film regime where surface energy significantly affects pattern formation, supported by experiments, simulations, and theoretical analysis.

Findings

Pattern length scale is approximately 3 times the film thickness for thick films.

Surface energy influences the pattern wavelength, especially in thin films.

A new regime where surface energy alters the instability wavelength is identified.

Abstract

Based on experiments and 3-D simulations, we show that a soft elastic film during adhesion and debonding from a rigid flat surface undergoes morphological transitions to pillars, labyrinths and cavities, all of which have the same lateral pattern length scale, close to \lambda/H ~ 3 for thick films, H > 1 micrometer. The linear stability analysis and experiments show a new thin film regime where \lambda/H \approx 3+ 2 (\gamma/3 \mu H)^(1/4) (\gamma is surface tension, \mu is shear modulus) because of significant surface energy penalty (for example, \lambda/H = 6 for H = 200 nm; \mu = 1MPa).