Graphene Oxide: An All-in-One Processing Additive for 3D Printing

Abstract

Many 3D printing technologies are based on the development of inks and pastes to build objects through droplet or filament deposition (the latter also known as continuous extrusion, robocasting, or direct ink writing). Controlling and tuning rheological behavior is key for successful manufacturing using these techniques. Different formulations have been proposed, but the search continues for approaches that are clean, flexible, robust and that can be adapted to a wide range of materials. Here, we show how graphene oxide (GO) enables the formulation of water-based pastes to print a wide variety of materials (polymers, ceramics, and steel) using robocasting. This work combines flow and oscillatory rheology to provide further insights into the rheological behavior of suspensions combining GO with other materials. Graphene oxide can be used to manipulate the viscoelastic response, enabling the formulation of pastes with excellent printing behavior that combine shear thinning flow and a fast recovery of their elastic properties. These inks do not contain other additives, only GO and the material of interest. As a proof of concept, we demonstrate the 3D printing of additive-free graphene oxide structures as well as polymers, ceramics, and steel. Due to its amphiphilic nature and 2D structure, graphene oxide plays multiple roles, behaving as a dispersant, viscosifier, and binder. It stabilizes suspensions of different powders, modifies the flow and viscoelasticity of materials with different chemistries, particle sizes and shapes, and binds the particles together, providing green strength for manual handling. This approach enables printing complex 3D ceramic structures using robocasting with similar properties to alternative formulations, thus demonstrating the potential of using 2D colloids in materials manufacturing.

3D printing with 2D colloids: designing rheology protocols to predict ‘printability’ of soft-materials

“…introduction of new functional, 4,[8][9][10][11] advanced and 2D materials 5,7,9,[12][13][14] with high added value and limited availability into a bespoke manufacturing technique to create on demand structures and devices. [8][9][10][11]15 It enables intricate parts for very specific applications to be created when a low number of parts are required, which would not be viable or affordable to make by other means.…”

“…[8][9][10][11]15 It enables intricate parts for very specific applications to be created when a low number of parts are required, which would not be viable or affordable to make by other means. Many efforts are being made in formulation design 5,9,[12][13][14]16 while the applications of this technique, for example in 3D printed batteries 15,17 and supercapacitors, 10,16 composites 12,[17][18][19] and hierarchical structures, 10,12 and bio-(3D)printing 12,[18][19][20] to name a few are steadily expanding. For many, the rapid growth promises a future where the 'imagination is the limit' but to actually get there, many challenges must be addressed from a multidisciplinary perspective.…”

“…For example, the requirements for DIW of glass and bio-printing are different to the needs in complex structures with high level of detail. In 3D-bioprinting inks must have relatively low yield stresses and storage moduli (G 0 ) in order to keep the cells alive; 12,14 this is also the case for glass formulations, where the stiffness of the inks is key for the successful post-processing stages, in order to avoid opacity and cracking. 14,20 On the other hand, many other applications in complex hierarchical structures require 'stiff' pastes that enable high printing resolutions to be achieved.…”

“…In 3D-bioprinting inks must have relatively low yield stresses and storage moduli (G 0 ) in order to keep the cells alive; 12,14 this is also the case for glass formulations, where the stiffness of the inks is key for the successful post-processing stages, in order to avoid opacity and cracking. 14,20 On the other hand, many other applications in complex hierarchical structures require 'stiff' pastes that enable high printing resolutions to be achieved. Despite the differences between these applications, it is generally recognised that printable formulations must be a shear thinning, yield-stress soft material exhibiting solid-like behaviour.…”

3D Printing of Tunable Energy Storage Devices with Both High Areal and Volumetric Energy Densities

“…[19] Due to the rich amphiphiles, stable dispersion capability and tunable rheological behavior, the graphene oxide (GO) is commonly selected to formulate multiple aqueous composite inks for extrusion-based 3D printing. [20] The rheological properties of the GO-based inks can be manipulated by adjusting the concentration of the ink and additives for different printing purposes, such as tuning formability, porosity, conductivity, and stability. Currently, diverse GO-based electrode structures including mesh, interdigitation and microlattice structures have been successfully constructed via the extrusion-based 3D printing.…”