Inkjet Printing of 2d Materials on Flexible and Rigid Substrates
2-dimensional (2d) materials such as graphene, transition metal carbides, nitrides, or carbonitrides (MXenes) and hexagonal boron nitride (h-BN) hold enormous potential for the next generation printable electronics. When these materials are formulated into inkjet printable inks, they can be incorporated with current inkjet printing technology. This strategy allows mask-less, large-area and low-cost deposition of 2d materials for next generation device fabrication. However, the current inks are far from ideal to support reproducible device manufacturing.
In this thesis, I present formulation of inkjet printable 2d material inks for thermoelectrics, conductive electrodes/circuits, touch sensors and capacitors applications. The graphene inks in this work are formulated via ultrasonic assisted liquid phase exfoliation (UALPE) of bulk graphite in isopropyl alcohol (IPA) with polyvinylpyrrolidone (PVP), followed by a centrifuge process. This allows one-step formulation of a polymer stabilised graphene ink. For MXene inks, I design a multi-solvent system for binder-free ink formulation. The formulated MXene inks show enhanced stability and suitable fluidic properties for inkjet printing.h-BN dielectric inks are formulated by two steps. First bulk h-BN is exfoliated via UALPE in N-Methyl-2-pyrrolidone (NMP). The exfoliated h-BN flakes are further collected via vacuum filtration and redispersed into 1-butanol/poly(4-vinylphenol) (PVPh) to formulated h-BN inks.
I demonstrate that all these inks have optimal fluidic properties, drying dynamics and interactions with substrates for spatially uniform, highly controllable and print-to-print consistent, enabling large-scale printing on both flexible and rigid substrates. These inks are further utilised to demonstrate large-area, flexible thermoelectrics, semitransparent conduct-ing circuits/electrodes and capacitors.
The successful demonstrations of these inks could facilitate the integration of different2d materials on one platform. This allows fabrication of all-printed transistors, circuits and capacitors for next generation printable electronics, resulting in a higher device integration and providing a promising solution for printable electronics.