Graphene as material with unique properties, shows high flexibility and durability. It also has high electrical and thermal conductivity combined with high optical transparency in visible light spectrum. Those properties amassed in single material make graphene the preferential material for modern electronics. One of its most promising applications is production of flexible, durable and transparent electrodes and conductive tracks. It has, among others, great significance in production of flexible screens and touch panels as well as OLEDs.

In this project printing inks and pastes, dedicated for production of transparent, flexible surfaces with inkjet and screen printing methods, will be developed. New technology of production of graphene-based printing dispersions will allow for creating overprints of dimensions as small as few microns, and with virtually no upper limitation regarding size. It will also significantly broaden the range of substrates compatible with overprinting of conductive surfaces. Those features make the project significant step in production of printed electronics and electronic clothing.

The main concept of this “Graphene-based inks and printing pastes production and printing method development for printed flexible electronics - GRAPHPRINT” is creating unique products dedicated for elastic electronics, printed with inkjet and screen printing methods. One of the most vital goals of this project is production of graphene-based dispersions with physical and chemical properties matching those of printing inks and pastes used for electronic element printing. Project also comprises optimization of technological parameters of inkjet and screen printing to allow for production of transparent conductive tracks with developed inks and pastes. Inkjet and screen printing methods are most promising and developmental techniques used to manufacture flexible electronics, mainly for production of thin conductive tracks on elastic polymer foil and textile s surfaces. Currently inks based on conductive organic compounds are used for this purpose. This solution, however, is not very effective because of very low charge carrier (μ<0.5cm2V−1s−1), but nonorganic nanomaterials might overcome those problems. Nowadays, technologies of production of inks and pastes based on dispersions, which contain silver nanoparticles, are being implemented, with carbon nanotubes as their only alternative. However, neither do those solutions ensure better charge carrier mobility values nor subsequently ensure high levels of transparency to created overprints. Those factors stand in a way of e.g. developing flexible touchscreens, solar cells, smart textiles or organic diodes, as both high carrier mobility and transparency are crucial in those applications.

Graphene, because of its exceptional properties such as very good electrical conductance, durability, flexibility and transparency of about 97% within whole visible light spectrum, can replace nanomaterials used for production of inks and pastes used nowadays. Physical properties of graphene allow for its great potential for applications in modern flexible electronics. Methods of graphene synthesis for flexible electronics used nowadays are mainly based on chemical deposition from gaseous phase (CVD) such as growth of the graphene on metallic substrates from carbon precursor. This method, however, requires very high temperatures and transferring of synthesized graphene onto arbitrary substrates with chemical dissolution, which significantly reduces capability of using elastic plastic substrates. Most recent research show that it is possible to make graphene coatings with inkjet method. It potentially increases the possibility of using graphene for practical applications, as it allows to print on a wide range of surfaces with high resolution, and may greatly reduce the cost of the coating. Currently developed inks and printing methods which employ various forms of graphene are still in research phase and currently do not allow for production of electrodes and surfaces with parameters close to those obtained with CVD. To fully exploit the potential of the graphene for printed, flexible electronics new printing compositions and overprinting methods, which would adapt widely used printing methods, need to be developed. It will allow to produce transparent, flexible, conductive surfaces and electrodes on various substrates, including elastic composite panels, foils and textiles. Shapes and dimensions of overprints will only be restricted by limitations in resolution of printing devices and pigment particle size.

Keeping guidelines of this project in mind, and taking into consideration the application of graphene to flexible electronics the following goals have been formulated:

• Production of printing compositions such as graphene-based inks and pastes, designed for production of flexible electronic elements.
• Development of printing methods allowing for production of transparent graphene electrodes and conductive tracks on selected elastic surfaces with widely used printing methods.
• Commercialization of both developed inks and technologies, by cooperating company.