LONDON – Researchers from the University of Cambridge have reported the ink-jet printing of graphene circuits, thereby demonstrating the suitability of graphene inks for flexible and transparent electronics. The simple use of a graphene-based ink and modified but standard ink-jet printers could bring closer the possibility of flexible, low-cost wearable computing devices, the researchers said.
The ink-jet printing of semiconducting polymer materials is well known for the large-area production of transistors, displays, photovoltaic devices, organic light emitting diodes (OLEDs). However, the electron mobilities of these materials are still much lower than standard silicon technology. The use of metal oxides and carbon nanotubes has been proposed to improve this but it usually comes at the cost of complexity in terms of adding stabilizer processes. By contrast graphene is a 2-D form of carbon in a single molecular layer that is the world's strongest and most conductive material.
The research team, led by Andrea Ferrari, made the ink by removing microscopic flakes from a block of graphite and suspending them in N-methylpyrrolidone (NMP). The use of NMP minimizes the "coffee mug ring" effect that occurs when some solvents evaporate. The team was able to print structures down to 90 -micron line widths and 90-nm thickness and below. The liquid-phase exfoliation (LFE)graphene-ink is described as a low-cost way to print thin-film transistors for flexible and transparent electronics.
The work was reported in the arXiv publication on condensed matter materials science.