From 2D to 3D: graphene moulding for transparent and flexible probes

Chemical vapor deposition (CVD) has been widely adopted as the most scalable method to obtain single layer graphene. Incorporating CVD graphene in planar devices can be performed via well established wet transfer methods or thermal adhesive release. Nevertheless, for applications involving 3D shapes, methods adopted for planar surface provide only a crude solution if a continuous, tear-free, wrinkle-free graphene layer is required. In this work, we present the fabrication and characterization of PDMS-supported 3D graphene probes. To accommodate 3D geometries, we perform CVD on catalysts possessing a non-trivial 3D topology, serving to mold the grown graphene to a final non-trivial 3D shape. This advance overcomes challenges observed in standard transfer processes that can result in uneven coverage, wrinkles and tears. To demonstrate the potential of our new transfer approach, we apply it to fabricate graphene electrical probes. Graphene, due to its flexibility, transparency and conductivity, is an ideal material with which to replace conventional metal based probes. In particular, with a contact resistance in the order of tens of kOhm, these graphene probes may find applications, such as in electrophysiology studies.