Rheological Issues in Carbon-Based Inks for Additive Manufacturing

Abstract

As the industry and commercial market move towards the optimization of printing and additive manufacturing, it becomes important to understand how to obtain the most from the materials while maintaining the ability to print complex geometries effectively. Combining such a manufacturing method with advanced carbon materials, such as Graphene, Carbon Nanotubes, and Carbon fibers, with their mechanical and conductive properties, delivers a cutting-edge combination of low-cost conductive products. Through the process of printing the effectiveness of these properties decreases. Thorough optimization is required to determine the idealized ink functional and flow properties to ensure maximum printability and functionalities offered by carbon nanoforms. The optimization of these properties then is limited by the printability. By determining the physical properties of printability and flow properties of the inks, calculated compromises can be made for the ink design. In this review we have discussed the connection between the rheology of carbon-based inks and the methodologies for maintaining the maximum pristine carbon material properties.

Keywords: additive manufacturing; carbon Inks; carbon nanotubes; graphene; printing; rheology.

Figure 1

Outline of various forms of carbon (C) used for inks in additive manufacturing and conventional printing techniques, along with their beneficial properties and potential uses.

Figure 2

Graphical representation of the general relationship of the conductivity trade-off with printability, in terms of tailoring conductive inks. The variables in the base triangle increase (particle size (μm), volume fraction (%), and purity (%)) the conductivity increases. Conversely, the printability increases with decreases in these variables.

Figure 3

Dependence of the flow behavior on pH level of graphene oxide (GO) in water lubrication, from this graph we observe the trend of higher friction being created. Taken from Aias et al. open access © University Malaysia Pahang Publishing, Malaysia [17].

Figure 4

General relationship of viscosity and shear rate, for flake suspension versus smooth sphere suspension (Sketch representation of the general trend concluded from Ran Niu et al. [19]).

Figure 5

Comparison of droplet volume to satellite volumes with increasing surface tension. As droplets are calculated by their diameter in additive manufacturing, the satellite droplets and tail are not accounted for and cause error. For effective printing, the closer the droplet can realize a spherical shape, the less the error.

Figure 6

Graphical representation of the idealized region for stable printing, where 1 < Z < 10, the inverse of the Ohnesorge number. The depicted blue area is the Goldilocks zone for 3D printing.