Adhesion Asymmetry in Peeling of Thin Films With Homogeneous Material Properties: A Geometry-Inspired Design Paradigm

Abstract

Peeling of thin films is a problem of great interest to scientists and engineers. Here, we study the peeling response of thin films with nonuniform thickness profile attached to a rigid substrate through a planar homogeneous interface. We show both analytically and using finite element analysis that patterning the film thickness may lead to direction-dependent adhesion such that the force required to peel the film in one direction is different from the force required in the other direction, without any change to the film material, the substrate interfacial geometry, or the adhesive material properties. Furthermore, we show that this asymmetry is tunable through modifying the geometric characteristics of the thin film to obtain higher asymmetry ratios than reported previously in the literature. We discuss our findings in the broader context of enhancing interfacial response by modulating the bulk geometric or compositional properties.

Quantitative peel test for thin films/layers based on a coupled parametric and statistical study

“…The lack of variation in phase 4 compared to the other phases was attributed to the change in peel mechanism. In phase 1 the tape was peeling directly off of the substrate and a roughly randomized failure of filaments of the adhesive layer at the peel front region caused variations in the peel force 35,36,45,48 . Similarly, phase 2 was an unstable phase with multiple modes of peeling and slightly changing angles due to the bubble under the film.…”

“…Three terms in above equation show works done by bending of peel arm, pull force, and adhesion energy respectively where ε is the potential energy, D ( s ) is the distribution of bending rigidity, and G is the constant adhesion energy. In addition to the peel angle ( θ ), the lengthwise angle of peel arm ( β ) is another significant factor on potential energy 36 which is corresponding to the peel front angle at s = 0 as represented in Fig. 3.…”