Delamination from an adhesive sphere: Curvature-induced dewetting versus buckling

Abstract

Everyday experience confirms the tendency of adhesive films to detach from spheroidal regions of rigid substrates—what is a petty frustration when placing a sticky band aid onto a knee is a more serious matter in the coating and painting industries. Irrespective of their resistance to bending, a key driver of such phenomena is Gauss’ Theorema Egregium , which implies that naturally flat sheets cannot conform to doubly curved surfaces without developing a strain whose magnitude grows sharply with the curved area. Previous attempts to characterize the onset of curvature-induced delamination, and the complex patterns it gives rise to, assumed a dewetting-like mechanism in which the propensity of two materials to form contact through interfacial energy is modified by an elastic energy penalty. We show that this approach may characterize moderately bendable sheets but fails qualitatively to describe the curvature-induced delamination of ultrathin films, whose mechanics is governed by their propensity to buckle and delaminate partially, under minute levels of compression. Combining mechanical and geometrical considerations, we introduce a minimal model for curvature-induced delamination accounting for the two buckling motifs that underlie partial delamination: shallow “rucks” and localized “folds”. We predict nontrivial scaling rules for the onset of curvature-induced delamination and various features of the emerging patterns, which compare well with experiments. Beyond gaining control on the use of ultrathin adhesives in cutting-edge technologies such as stretchable electronics, our analysis is a significant step toward quantifying the multiscale morphology that emerges upon imposing geometrical and mechanical constraints on highly bendable solid objects.

Pattern Formation in Confined Core‐Shell Structures: Stiffness, Curvature, and Hierarchical Wrinkling

“…Thermal stress, applied during the metal deposition step by thermal evaporation, acts as an additional factor that increases the degree of confinement. This additional stress leads to a range of outcomes, from the coexistence of unwrinkled regions and radial wrinkles, as documented in geometrically incompatible confinement studies, [23,[26][27][28] to complex patterns in core-shell microspheres. [29][30][31][32][33] Additionally, a new type of pattern synchronization is observed, consisting of either dimple or buckyball patterns on curved surfaces decorated with hierarchical wrinkles at the edges.…”

Growth-induced delamination of an elastic film adhered to a cylinder

“…Although, for example, the formation of a wrinkle on a bottle label has trivial consequences, the delamination of thin films becomes a more significant issue for coating technologies such as stretchable electronics [1][2][3]. Thus, understanding the mechanics of adhesive sheets becomes crucial for applications, but also provides an interesting mathematical paradigm in which mechanics of slender bodies, adhesion properties and substrate geometry meet [4].…”