The Liquid Blister Test

TL;DR

This study investigates how a thin elastic sheet detaches from a substrate under vertical displacement, forming different blister shapes, and develops a theoretical model that matches experimental observations based on elastic and capillary forces.

Contribution

The paper introduces a theoretical framework predicting blister shapes in elastic sheets adhering via liquid surface tension, validated by experiments.

Findings

Perimeter of blisters transitions from circular to undulating to triangular with increasing displacement.

Theoretical predictions align well with experimental data.

Different blister shapes are governed by distinct elastic-capillary force balances.

Abstract

We consider a thin elastic sheet adhering to a stiff substrate by means of the surface tension of a thin liquid layer. Debonding is initiated by imposing a vertical displacement at the centre of the sheet and leads to the formation of a delaminated region, or `blister'. This experiment reveals that the perimeter of the blister takes one of three different forms depending on the vertical displacement imposed. As this displacement is increased, we observe first circular, then undulating and finally triangular blisters. We obtain theoretical predictions for the observed features of each of these three families of blisters. The theory is built upon the F\"{o}ppl-von K\'{a}rm\'{a}n equations for thin elastic plates and accounts for the surface energy of the liquid. We find good quantitative agreement between our theoretical predictions and experimental results, demonstrating that all three families are governed by different balances between elastic and capillary forces. Our results may bear on micrometric tapered devices and other systems where elastic and adhesive forces are in competition.