Adhesion of heterogeneous thin films II: Adhesive heterogeneity

This paper continues the study of the effective adhesion of thin films on rigid substrates in the presence of spatial heterogeneities started in Xia et al. (2013). In this paper, we focus on thin adhesive tape with spatial heterogeneity in the adhesive strength. This heterogeneity leads to a wavy peel front and consequently a complex corrugated shape in the tape. We develop a theory for the evolution of the peel front that accounts for this complex interaction, and an experimental method that is able to examine this in detail. We show through theory and experimentation that spatial patterning of the adhesive strength can lead to a very rich range of behaviors in the effective adhesive strength. In particular we show that adhesive heterogeneity can be used to create asymmetry in that the force required to peel the tape in one direction can be different from that in the other.