The stiff and brittle indium tin oxide (ITO) is by far the most widely used material for producing transparent conducting coatings for electronic devices. Nevertheless, as raw materials for ITO are becoming increasingly expensive and more importantly due to its rigidity, the industry today faces the challenge of replacing the conventional brittle ITO with a flexible, yet robust, transparent but also conductive material. Graphene combines the aforementioned properties, therefore it is considered as the most promising candidate for substituting ITO. Graphene consists of a two-dimensional (2D) hexagonal lattice made of sp2 hybridized carbon atoms. The structure and hybridization of graphene result in its extraordinary mechanical properties and its high electrical and thermal conductivity, thanks to an extended conjugated system of π delocalized electrons. On the other hand, to date, the market of printed electronics is based on Ag inks/pastes. However, Ag can be expensive. Ag nanoparticles have poor adhesion, while other Ag forms, such as nanowires or flakes exhibit further processing difficulties and surface roughness. Printed Cu develops an insulating oxide layer, while other metals, carbon or polymers have average conductivity. Graphene has good conductivity and is emerging as a potential Ag substitute for printed electronics, to be used in wearable devices, e-paper, roll-up portable or/and transparent displays, etc.
The overall objective of NanoGraphInk was the development of fully applicable and viable conductive nano-hybrid graphene-based inks and pastes for printable applications and device fabrication. In addition, aiming at non-toxic final products, emphasis was placed in developing inks and pastes based on environmentally friendly solvents such as water, alcohols, or further non-toxic organic media. By controlling composition, rheological properties, possible compatibility issues, and other parameters, these materials can be enabled for use in diverse industrial applications. Thus, given the cost of ITO for electronics and of Ag for printed electronics, NanoGraphInk aimed at the production of low-cost substitutes suitable for easily implementable, direct industrial application.
