Adhesion-induced fingering instabilities in thin elastic films under strain

TL;DR

This paper investigates how pre-strain in thin elastic films influences the formation and anisotropy of adhesion-induced fingering patterns during contact with a spherical indenter, combining experimental observations with modeling.

Contribution

It introduces a quantitative analysis of anisotropic fingering patterns caused by pre-strain and develops a simple model explaining the anisotropy's origin.

Findings

Fingering patterns become anisotropic under pre-strain.

The characteristic wavelength of fingers remains consistent.

A model explains the transition from isotropic to anisotropic patterns.

Abstract

In this study, thin elastic films supported on a rigid substrate are brought into contact with a spherical glass indenter. Upon contact, adhesive fingers emerge at the periphery of the contact patch with a characteristic wavelength. Elastic films are also pre-strained along one axis before initiation of contact, causing the fingering pattern to become anisotropic and align with the axis along which the strain was applied. This transition from isotropic to anisotropic patterning is characterized quantitatively and a simple model is developed to understand the origin of the anisotropy.