A Cu Leaf Enabled Polymer-Free Patterning of Graphene as Flexible Circuits.

Chemical vapor deposition (CVD)-grown graphene holds excellent promise for advancing electronic devices. However, traditional graphene patterning methods, which often involve polymer-assisted transfer and photoresist-based lithography, are hindered by polymer residues and process complexity. Here, we introduced a polymer-free approach that combines metal leaf-assisted techniques with laser printing to fabricate diverse graphene patterns (GPs) rapidly and economically on flexible substrates, such as paper and polyethylene terephthalate (PET). Multilayer graphene was synthesized on Cu leaves via plasma-enhanced CVD, and the inherent flexibility of the Cu leaves enabled conformal contact between the graphene film and target substrates. By exploiting substrate-specific adhesion mechanisms─thermally activated bonding to laser-printed toner regions and ethanol-mediated capillary forces combined with pressure-enhanced adhesion on paper and PET substrates, respectively─graphene was selectively transferred at a resolution of 200 μm. When integrated with light-emitting diodes, the resulting graphene pattern circuits showed linear current-voltage responses and robust stability across varying bending curvatures. This study provides a facile and cost-efficient pathway for directly fabricating GPs on flexible substrates, potentially accelerating the development of graphene-based flexible devices.