Patterning of carbon nanotube structures by inkjet printing of catalyst

The controlled deposition of carbon nanotubes (CNTs) has many potential applications in areas such as microfluidics and field emission arrays. The use of inkjet printing to deposit catalyst offers numerous advantages for these, particularly the ability to print arbitrary patterns at low cost. We use inkjet technology to deposit iron salts, which act as a catalyst from which CNTs are subsequently grown by chemical vapour deposition. In this study, we study the effect of the iron salt concentration on ink viscosity, as well as the printing quality using optical and electron microscopy. We find that the iron salt concentration has a significant effect on the pattern quality and, most importantly, allows for the production of controllable ring-like shapes with feature size smaller than that achievable by the print-head alone. These shapes are the result of a variation of the coffee-stain effect, and could be useful particularly in fabricating microfluidic devices. We show that iron salts are suitable CNT catalysts for deposition by inkjet printing, and that their concentration is crucial both for print quality as well as for the production of novel patterns by making use of the drying behaviour of the ink.