Controllable Buckle Delaminations in Polymer-Supported Periodic Gradient Films by Mechanical Compression

Abstract

Surface instabilities including wrinkles and buckle-delaminations are widespread in nature and can be found in a wide range of practical applications. Compared with the homogeneous wrinkle mode, the buckle-delaminations are spontaneously stress-localized, and their initiation positions and geometrical parameters are hardly precisely controlled by a simple method. Here, we report on the controllable buckle-delaminations in periodic thickness-gradient metal films on polydimethylsiloxane (PDMS) substrates by uniaxial mechanical compression. It is found that a periodic thickness-gradient film is spontaneously formed by masking a copper grid during deposition. The released mechanical strain tends to concentrate in thinner film regions, resulting in the restricted growth of buckle-delaminations. The geometrical features, evolutional behaviors, and underlying physical mechanisms of such buckle-delaminations are analyzed and discussed in detail based on the buckling model and finite element simulations. This work would provide a better understanding of the restricted buckle-delaminations in heterogeneous film–substrate systems and controllable fabrication of ordered structural arrays by copper grid masking and mechanical loading.

Coexistence and Coevolution of Wrinkle and Ridge Patterns in the Film–Substrate System by Uniaxial Compression

“…Therefore, once the localized ridge initiates at a certain position, it can spontaneously propagate to form a stable structure with large amplitude, as shown in Figure . This situation is similar to other localized patterns such as cracks, buckle-delaminations, and creases. ,− Note that the ridge formation can be viewed as a snapping process, as shown in Figures and . The wrinkled or even flat film surface can abruptly bump up to a certain height .…”

“…Localized patterns can be widely observed in natural and artificial systems. For example, the tensile strain leads to the formation of localized cracks in brittle materials such as drying mud, coatings, and films. , The compressive strain leads to the formation of localized buckle-delaminations in elastic films on rigid substrates. , For soft elastic substrates, the coexistence of sinusoidal wrinkles and localized buckle-delaminations can be observed if the interfacial adhesion is comparatively weak. − For liquid or very soft substrates, the elastic films tend to form sinusoidal wrinkles under modest compression and localized folds, ridges, or period-doubles at large strain. For pure soft materials such as gels, hydrogels, and biological tissues, localized creases are observed under large compression …”