Graphene’s flexibility, optical transparency and electrical conductivity make it suitable for a range of applications. Although numerous laboratory prototypes have been demonstrated around the world, widespread commercial use of graphene is yet to be realised.
Dr Tawfique Hasan of the Cambridge Graphene Centre (CGC), said: “We are pleased to be the first to bring graphene inks close to real-world manufacturing. There are lots of companies that have produced graphene inks, but none of them has done it on a scale close to this.”
Hasan’s method is said to work by suspending tiny particles of graphene in a ‘carrier’ solvent mixture, which is added to conductive water-based ink formulations. The ratio of the ingredients can be adjusted to control the liquid’s properties, allowing the carrier solvent to be mixed into a conventional conductive water-based ink to reduce the resistance. The same method works for materials other than graphene, including metallic, semiconducting and insulating nanoparticles.
Currently, printed conductive patterns use a combination of poorly conducting carbon with other materials, most commonly silver, which is expensive. Silver-based inks are said to cost £1000 or more per kilogram, whereas the graphene ink formulation is claimed to be 25 times cheaper. Additionally, graphene and other carbon materials can be recycled whereas silver cannot. The new method uses cheap, non-toxic and environmentally friendly solvents that can be dried quickly at room temperature, reducing energy costs for ink curing. Once dry, the ‘electric ink’ is also waterproof and is said to adhere well to its substrate.
The graphene-based inks have been printed at a rate of more than 100m per minute, which is in line with commercial production rates for graphics printing, and faster than earlier prototypes.
Hasan’s group tested the method on a typical commercial printing press, which required no modifications in order to print with the graphene ink. In addition to the new applications the method will open up for graphene, it could also initiate entirely new business opportunities for commercial graphics printers, who could diversify into the electronics sector.
“The UK has always been strong in the printing sector, but mostly for graphics printing and packaging,” said Hasan. “In addition to cheaper printable electronics, this technology opens up potential application areas such as smart packaging and disposable sensors, which to date have largely been inaccessible due to cost.”
In the short to medium term, the researchers hope to use their method to make printed, disposable biosensors, energy harvesters and RFID tags.
