Printed Graphene-based Interconnects and Vias for Flexible Hybrid Electronics

Graphene-based inks are emerging as a mechanically resilient alternative to silver and copper nanoparticle systems for printed interconnects in flexible hybrid electronics (FHE). Unlike brittle metallic films, graphene flake networks survive repeated bending through crack bridging and percolation reconfiguration. However, the intrinsic-to-practical conductivity gap remains the central challenge: inter-flake junction resistance places printed film conductivity orders of magnitude below bulk metals. This review examines graphene ink formulation, covering liquid-phase exfoliated, electrochemically exfoliated, and reduced graphene oxide sources, along with inkjet, aerosol jet, screen printing, gravure printing and Electrohydrodynamic (EHD) printing strategies. Via formation, largely overlooked in existing literature, receives dedicated treatment covering sidewall coverage, aspect ratio constraints, and hybrid graphene–metal approaches. Conductivity enhancement routes, mechanical fatigue under cyclic bending, and integration with thinned silicon dies are also discussed. This review offers practical guidelines for ink selection, printing optimization, and via engineering in FHE.