Inkjet Printing of Inks of Large Flakes of Reduced Graphene Oxide

  • Wentao Zou

Student thesis: Phd

Abstract

The graphene-related materials frequently used for flexible and transparent electrodes (FTEs) — graphene oxide (GO) and graphene nanoplatelets — suffer from the insulating nature or the limited flake size, which degrades the electrical conductivity and limits the available range of substrate of FTEs. Another derivative of graphene, reduced graphene oxide (rGO), is used in the project due to its relative advantages in conductivity and flake size compared to the other two materials. This project aims to use the advantages of this material to prepare a series of novel inkjet printable large rGO inks, which can overcome the above challenges at the same time. This project also aims to be the first to formulate this type of ink with water as the main solvent which make the ink more eco-friendly as well. In this project, we used a team-made polyaromatic hydrocarbon stabiliser to prepare large rGO water-based inks due to its high stabiliser/graphene ratio and check inkjet printability of these inks on the picolitre printhead based on the reported inkjet printability of ultra-large GO flakes through similar type of printhead in microlitre. Then, advantages of rGO could be applied in the preparation of printed FTEs with higher resolutions. During the printing of these rGO inks, a new waveform was developed to suppress the satellite issue due to their rheological properties. Two unique drying issues were observed during exploration, missing front and waviness (in printed squares only). The first dot problem, which is common in inkjet printing leads to the first issue. The dual-ring structure with a depletion zone in dried dot, which causes miss setting of drop spacing is the key of second issue. The satellites issue can be suppressed by adding an extra filtering step before printing. To supress the waviness, the effects of printer settings, ink formulations, and substrate treatments on droplet drying were investigated. The strong Marangoni effect is the critical factor causing this unique structure and it can be controlled by optimising ink formulation and substrate treatments. Then, a guide of how to prepare this new type of rGO ink without major issues was concluded in this project. Finally, it was the first time that DMC-11610 printhead successfully printed a rGO water-based ink with average flake size up to 1.5 μm. This achievement expands the potential of rGO as a functional material for future printed FTEs.
Date of Award31 Dec 2023
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorMichael Turner (Supervisor) & Aravind Vijayaraghavan (Supervisor)

Keywords

  • Graphene
  • Inkjet printing

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