Measuring adhesion of soft elastic shells

Adhesion of soft materials is commonly measured through the classical JKR framework where a full elastic hemisphere is slightly compressed on a flat plane. However, this technique is not suitable for highly compliant materials or structures for which deformations become non-linear. Here we experimentally explore an alternative approach, inspired from the compliance method originally developed for fracture mechanics and based on the measurement of the work of adhesion during an indentation cycle. We illustrate this technique with elastomeric hemispherical shells and propose an extension to non axisymmetric shapes. Although the involved forces are of the same order of magnitude as in a standard JKR test, the corresponding displacements are much larger and can thus be more easily controlled. Precise measurements of adhesion then become possible on samples of arbitrary shape or internal structure and materials with non-linear elastic response.