Figure 1.

Fabrication process and morphology characterization of wrinkled graphene-based multilayer films. (A) Illustration of the fabrication process for wrinkled GO multilayer films. (B) Demonstration of reversibility by re-stretching under an optical microscope, scale bar is 100 μm. (C) AFM image showing the basic morphology of parallel ridges with sharp crests (light) and broader valleys (dark). Film thickness is 20 nm and scale bar is 20 μm. (D) SEM showing longitudinal microcracks that form when simple uniaxial relaxation occurs (left image). These cracks can be suppressed (right image) if the substrate is constrained in the transverse direction during relaxation to prevent the expansion associated with the Poisson effect, scale bar 100 μm. (E) High-tilt SEM image of transverse profiles, which shows a delaminated buckle structure with nearly straight slopes (arrow 1) and curvature concentrated at the ridge tops (arrow 2). These wrinkles are high-amplitude buckled ridges in which some primary peaks have collapsed on neighbors to create double-ridges (arrow 3). Scale bar 20 μm. All samples in Fig. 1 unless noted use 50% pre-stretch and 200 ug/ml GO suspension that gives a nominal GO film thickness of 200 nm).