Self-assembly of graphene nano-particles on biocompatible polymer through dewetting

In this work, we present the formation of unique self-assembled graphene patterns at the interface between graphene and a thin polystyrene (PS) film at room temperature. When a minute amount of graphene dispersed in a solvent is added on PS and spin-coated into a thin film, the concentration gradient caused by centrifugal force leads to a Marangoni flow that in conjunction with the dewetting of the underlying PS at the edges lead to a series of very interesting and self-assembled morphologies of graphene. At the particle enriched zone near the center, the graphene-particles exhibit morphologies ranging from folds, wrinkles, flakes, onion-rings to blob structures depending on the aspect ratio. The graphene-particles thrown to the periphery are found to march back towards the central portion leading to the unique formation of very ordered nano-scale scratches on the PS substrate. The nano-particles that end up into the confined rims in the intermediate region get twisted into nano-ribbons and dendrimers. The paper sheds light on the forces responsible for the evolution of different origami structures formed as a result of the underlying dewetting dynamics without the aid of any high-end instrumentation or process. Since these self-assembled structures are formed over a bio-compatible polymer, the structures are anticipated to find applications in fabricating biosensor, super-capacitors, and biomedical microfluidic devices.