Experiments with Graphene-Reinforced Nanocomposites in DLP 3D Printing

In ‘Fabrication of Graphene-Reinforced Nanocomposites with Improved Fracture Toughness in Net Shape for Complex 3D Structures via Digital Light Processing,’ authored by Chinese and UK authors, the question remains as to whether digital light processing can be used to create a facture toughness specimen without numerous notch preparation steps—and affordably so.

DLP is a vat-polymerization-based 3D printing method popular with many researchers, and one like SLA—except that objects are created in a layering process instead of point by point. Here, the authors had a keen interest in nanocomposites, exploring the potential for improving mechanical properties in parts, despite limited use with such materials in DLP so far. Historically, this has been due to challenges presented by nanoparticles during 3D printing.

Schematic procedures of the preparation process for graphene-reinforced nanocomposites.

“The resin viscosity and subsequent printability could be affected when nanoparticles, such as graphene, with large surface areas are introduced. The presence of graphene could also block UV light, thus interfering with the photocuring process of resin,” stated the authors.

Previous researchers have encountered issues with viscosity ‘hindering printing,’ although the authors remain positive about using DLP for curing of nanofiller resins.

“It is also worth noting that with DLP 3D printing, nanocomposites can be fabricated into a net shape directly without multistep molding, cutting, and other steps, which could be utilized to make complexly shaped structures with improved properties,” state the researchers.

In the course of this research, the team developed their own resin that relies on UV curing, and includes graphene-reinforced nanocomposites (GNPs). Ultimately, they were able to complete a 3D print with a complex geometry—without using solvents. They also reported success with high resolution and reproducibility, accompanied by affordability.

“A gyroid scaffold for tissue engineering applications based on current GNP nanocomposite resins has been successfully fabricated via DLP, demonstrating the suitability of current resins for complexly shaped structures as well as potential for applications in various fields such as bone tissue engineering,” stated the authors.

Viscosity continued to be a major consideration throughout the project, and the researchers considered to notice the challenges in setting parameters, with low viscosity required for DLP printing (as well as SLA). If viscosity became too high, there was the possibility for deformation or complete failure. Along with viscosity characterization and examination, the authors were also aware of how thermomechanical properties affected the process, ‘confirming no obvious effect on the printability or the photocuring process…’

The research team noted relative ‘homogeneous nanofiller dispersion’ during the rapid curing, along with an improvement of mechanical properties with only 0.5 wt. percent, showing a 14 percent increment in flexural modulus and a 28 percent improvement in fracture toughness.

Success was achieved in terms of creating numerous specimens, ‘indicating the effectiveness of using the current method to perform rapid trials on new formulations with improved fracture toughness.’

“With the developed graphene-reinforced resins, 3D complex structures including a jawbone with a square architecture as well as gyroid scaffold for bone tissue engineering applications were successfully fabricated via DLP, showing the great potential of current UV-curable nanocomposite resin systems for various applications in fields such as bioengineering,” concluded the researchers.

Images of (a) pure UV-cured resin with a square architecture and (b) a close view of the circled area in (a), showing smooth surface finish with relatively high resolution. Images of (c) pure UV-cured resin and (d) graphene-reinforced nanocomposite gyroid scaffold for bone tissue engineering.

Whether you are a manufacturer, serious innovator, or a hobbyist just thinking about purchasing your first 3D printer, you may be surprised to find out how much thought goes into materials. And for those who are serious about making strong new prototypes and parts, if they don’t have what they need—let the experimenting begin! This is the case in workshops and labs around the world, whether users are busy testing out clay composites, combinations of titanium and ceramic, or even wood. Find out more about graphene nanocomposites here.

(a) Schematic of the digital light processing (DLP) process. Photographs of flexural test specimen (b) references without graphene and (c) with 0.5 wt.% graphene. Photographs of fracture toughness test specimens (d) without graphene and (e) with 0.5 wt.% graphene.