Delamination-Free Functional Graphene Surface by Multiscale, Conformal Wrinkling

Obtaining a delamination-free wrinkled functional graphene surface in layered systems is an interesting challenge because the interface is usually too weak to withstand interfacial stress mismatch, which can trigger mechanical instability. In this paper, a general strategy is proposed toward addressing the delamination limitation imposed by fabricating conformal graphene wrinkles with bilayer systems of poly(methyl methacrylate) (PMMA) and polydimethylsiloxane (PDMS). To improve the interfacial strength, a postcuring transfer process is introduced to form a gradient interface layer without interfacial liquid between the PMMA and PDMS by entanglement of polymer chains during high-temperature curing. Compared to the conventional wet transfer of graphene,the transfer method can greatly enhance the interfacial strength. The chemical and mechanical mechanisms underlying the enhancement are revealed both experimentally and theoretically in terms of the transition from the buckled-induced delamination state to the delamination-free wrinkled state. Moreover, the light diffraction behaviors of multiscale graphene wrinkles are initially demonstrated to be an interesting continuous pattern induced by overlapping. The delamination-free conformal wrinkled functional graphene surface can provide valuable insight and design guidelines for the fundamental problems of deformed graphene and its applications in flexible functional devices.