Harnessing strong and asymmetric adhesion by combining film heterogeneity and substrate morphology

Abstract

We use a combined theoretical and experimental approach to investigate the quasi-static peeling behaviors of heterogeneous films from corrugated substrates. The heterogeneity is involved in films through two different methods, i.e., local stiffening and kirigami patterning, and the substrate surface is assumed to adopt a sinusoidal profile. Our results show that the spatial variation in film's bending stiffness, caused by the elastic heterogeneity with period form, can significantly enhance the peak peel force and give rise to asymmetric adhesion performance. The substrate's roughness can further amplify such adhesion enhancement and asymmetry by affecting the local peel angle at the peel front. The adhesion performance depends sensitively on the relative position between the heterogeneous films and corrugated substrates, and our results show that a combination of film heterogeneity and substrate undulation can enhance the adhesive strength by more than 100 times, compared with the case of homogeneous film and flat substrate. This study provides a theoretical framework to reveal multiple peeling mechanisms in the problem and can guide the design of film-substrate systems with tunable and anisotropic adhesion.