3D printing amphiphilic graphene polymer composites for high performance applications

• Main Author: Wee, Jonathan Jianwei
• Other Authors: Paulo Jorge Da Silva Bartolo
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2024
• Subjects: Engineering; 3D printing; Graphene; Graphene composite
• Online Access: https://hdl.handle.net/10356/177790
• Institution: Nanyang Technological University

Karbohm (mGO) is a modified graphene oxide that encompasses the exceptional mechanical, thermal, and electrical properties of graphene which are typically lost when graphene is oxidised. This study explores the material development of mGO inks for extrusion-based direct ink writing by evaluating the use of ionic cross-linking as a gelation method for printing mGO inks, assessing the compatibility of mGO with CNC and CNF composites, and determining the optimal dispersion mechanism for both the ionically modified mGO-CaCl2 inks and mGO cellulose composite inks. Building on this foundation, printability studies were conducted to optimise the printing parameters, which will ensure high resolution and strong structural integrity of the prints. Additionally, the viability and potential applications of the inks were also explored through further characterisation to analyse the morphology, electrical and mechanical properties. Further extending these analyses, to evaluate the effects of different manufacturing techniques on the properties of the samples, the ionically modified mGO-CaCl2 inks, and mGO-CNC and mGO-CNF composite inks were printed and cast. The samples were then dried at room and oven (60°C) temperature to examine the effects of different post-processing drying methods on the properties of the samples. However, challenges were faced during the printing process of the ionically modified mGO-CaCl2 inks as the extrusion rate could not be controlled due to the uneven dispersion of mGO in the inks. Nonetheless, the mGO-CNC and mGO-CNF composite inks showed higher success in achieving uniform extrusion rates that resulted in accurate prints. The results from the study showed that the resistivity of the ionically modified mGO-CaCl2 cast samples were 5 orders of magnitude lower as compared to the mGO-CNC and mGO-CNF composite samples. Additionally, the drying of the samples at oven (60°C) temperature affected the samples differently. The ionically modified mGO-CaCl2 samples dried at oven (60°C) temperature had lower resistivity compared to the ionically modified mGO-CaCl2 samples dried at room temperature while the mGO-CNC and mGO-CNF composite samples dried at oven (60°C) temperature had higher resistivity compared to the mGO-CNC and mGO-CNF composite samples dried at room temperature. Furthermore, the mGO-CNF composite samples dried at oven (60°C) temperature recorded higher values for ultimate tensile strength but lower values for elongation at break. Increase in mGO concentrations across the samples also led to increases in ultimate tensile strength, except for the mGO-CNC composite samples dried at oven (60°C) temperature that showed a different stress-strain curve from the mGO-CNC composite samples that were dried at room temperature. The results from this study have established a basis for future research and applications that involves the use of mGO in extrusion-based direct ink writing. Future research could expand upon the findings of this study to optimise the composition of mGO and CNC/CNF, striving for a balance between mechanical strength, flexibility, and conductivity. Such developments could have significant applications in the field of soft electronics.