Gecko-inspired dry adhesives for heritage conservation - tackling the surface roughness with empirical testing and finite element modelling

Gecko-inspired dry adhesives (GDAs) have been developed in an attempt to replicate in polymer material the natural ability of some gecko lizards to attach to nearly any surface. Geckos achieve this with nano-sized structures on their feet that facilitate van der Waals's interactions with the surfaces. The conservation of cultural heritage is an area that could benefit greatly from the introduction of a versatile and easily reversible adhesive. However, the multitude of surface types and various surface textures encountered in this field make the adaptation of GDAs difficult. In this research two types of GDAs, with flat tips and with mushroom-shaped tips have been assessed using pull-off tests on three substrate materials. These are based on real heritage objects' surfaces (copper and ceramic) with different levels of surface roughness from The Hunterian collection. Adhesive strength varied between different GDAs and as expected adhesive strength reduced with increased substrate roughness. The finite Element Modelling (FEM) of the pull-off tests closely matched empirical results and showed how different behaviours on the microlevel can affect the GDA behaviour on rough surfaces. It helped to understand the microscale behaviour of two different types of GDAs tested. The research has shown the necessary direction for experimental and theoretical research on GDAs which will enable them to be adopted more widely in heritage conservation.