Liquid-phase exfoliation of two-dimensional graphite for ink-jet printing
Over the last decade, the study of two-dimensional (2D) materials has seen an incredible growth due to their unique thermal, mechanical and electronic properties. Solution phase manufacturing offers a way in which they can be produced at large scale by creating dispersions from the exfoliated material. Once created, different options for assembling devices exist. One technique for large scale manufacturing of materials in this form is ink-jet printing, which is a form of additive manufacturing that has proven to be attractive for the printed electronics industry. One challenge that ink-jet printing still faces is the shortage of inks with appropriate properties, since there are many parameters that affect the success of the printing process in general. In this work, we have developed techniques for the exfoliation of bulk crystals and optimized the properties of the inks so that they are suitable for inkjet printing. Dispersions have been produced and printed successfully by preparing both surfactant–assisted and surfactant–free inks. We have analyzed the effect of some printing parameters such as varying the number of nozzles that are used for printing, the number of passes or layers printed and the annealing conditions, and characterized the structure and electronic transport properties of the printed features. The prepared inks have been printed on rigid SiO2/Si substrates, as well as transparent and flexible polyimide substrates. The pattern printed on the polyimide was tested as a function of bending, which shed insights into the mechanical elasticity and adhesion of the printed features to the substrate with minimal changes in electrical transport properties, indicating that such structures are ideally suited for flexible electronics. In addition, high power resistor structures have been fabricated that demonstrated outstanding power with levels of up to 7 W being delivered by the printed resistive structures. Furthermore, the resulting prepared inks have shown very little variation in resistance values over a wide range of temperatures allowing them to be used in extreme thermal environments where a nearly flat temperature coefficient of resistivity may be desired. This work shows great promise of ink-jet printed nanomaterials, and has shed insights into understanding the properties of the printed structures for electronics and flexible electronics applications.^
Michel Parra, Monica, "Liquid-phase exfoliation of two-dimensional graphite for ink-jet printing" (2016). ETD Collection for University of Texas, El Paso. AAI10248403.