The method uses a conventional roll-to-roll printing process, similar to printing newspapers and crisp packets.

Potential applications include inexpensive printed electronics, intelligent packaging and disposable sensors.

The researchers found that graphene and other electrically conducting materials could be added to conventional water-based inks and printed using typical commercial equipment. This is the first time that graphene has been used for printing on a large-scale commercial printing press at high speed.

Graphene is a two-dimensional sheet of carbon atoms that is one atom thick. Graphene characteristics include flexibility, optical transparency and electrical conductivity which make it suitable for various applications, including printed electronics.

While many prototypes using graphene have been demonstrated worldwide, widespread commercial use of graphene is yet to happen.

“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,” says Dr Tawfique Hasan of the Cambridge Graphene Centre (CGC), who developed the method. “Being able to produce conductive inks that could effortlessly be used for printing at a commercial scale at a very high speed will open up all kinds of different applications for graphene and other similar materials.”

Hasan’s method works 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 easily mixed into a conventional conductive water-based ink to significantly 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 and other materials like expensive silver. Silver-based inks cost over $1,500 or more per kilogram, but this new graphene ink formulation would be 25 times cheaper.

Another downside to using silver is that it is not recyclable, while graphene and other carbon materials can easily be recycled. The new method uses inexpensive, 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 adheres to its substrate extremely well.

The graphene-based inks have been printed at a rate of more than 100 meters per minute (m/m), in line with commercial production rates for graphics printing, and much faster than earlier prototypes.

This is not the first time Hasan and his colleagues have worked with graphene-based inks. Two years ago, they produced a prototype of a transparent and flexible piano using graphene-based inks, which took between six and eight hours to make. After using the new ink, they found that more versatile devices on paper or plastic can be made at a rate of 300 m/m, at a very low cost.

Hasan and students Guohua Hu, Richard Howe and Zongyin Yang of the Hybrid Nanomaterials Engineering group at CGC, 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, and the Cambridge area in particular, has always been strong in the printing sector, but mostly for graphics printing and packaging,” says Hasan. “We hope to use this strong local expertise to expand our functional ink platform. 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 near future, the researchers would like to use the new method to print disposable biosensors, energy harvesters and radio frequency identification tags.

For more information visit the University of Cambridge.