HiGRAPHINK aimed to develop cost-effective graphene-based inks as additive to organic polymer inks, outperforming currently used semiconducting polymers, and to demonstrate the manufacturability and scalability of graphene-enhanced thin film transistors (TFTs) and vias. HiGRAPHINK developed a new microfluidic processing to produce graphene and related material inks on a large scale (2 L per day at lab scale and 220 L per day at industrial scale). These inks can be used to print conductive tracks competitive with copper and silver, but with cheap, simple and scalable procedures. This opened up many new avenues, with applications ranging from batteries, to printed circuit boards, composites and antennas. A patent application was submitted and the technology was licensed to Cambridge Graphene Ltd (CGL). CGL has already commercialized these products. These inks are also sold through one of the world’s biggest chemical suppliers, Sigma-Aldrich (now Merck). Numerous companies are in touch to explore the potential of these novel inks. In January 2017, Versarien plc. acquired 85% of CGL and invested a significant amount in the new company. The next steps for CGL are to validate a pilot scale production from the proven novel, repeatable, microfluidisation process at lab-scale.
The exfoliation of other layered materials (insulating hexagonal boron niride, h-BN, and semiconducting transition metal dichalcogenides, TMDs) was also studied for the production of inkjet printable inks with complementary properties. Microfluidization of h-BN allows the production of stable dispersions in water with concentration up to 1 g/L. The dielectric properties of the h-BN inks were evaluated in printed metal-insulator-metal capacitors. A dielectric constant for pin-hole free h-BN film (100nm thick) up to~ 6.92 and capacitance per unit area~1nF/mm2 were achieved. The same inks were used to print a top gate in graphene TFTs. Mobilities up to 110 cm2/V.s were achieved. The TFTs showed good flexibility with >90% of the initial mobility restored after 1.5% bending strain (5mm bending radius).
The success of this project will bring economic return throughout the supply chain.
