Could this LCP-based bioinspired technique be a game-changer for FDM 3D printing?

While some still perceive FDM (or FFF) 3D printing as a low cost and relatively low quality additive manufacturing process, many are quickly seeing the potential of the technology and are working towards improving it on all fronts: hardware, software and materials. A team of researchers from ETH Zurich recently made a significant breakthrough with FDM with a new, bioinspired approach to 3D printing recyclable liquid crystal polymers (LCPs).

The new technique, which uses a common polymer material and a commercial FDM 3D printer, has the potential to manufacture parts that outperform existing printed polymers and compete with some of the highest performance lightweight materials. Because the approach is so accessible in terms of its materials and hardware, the researchers believe it could be a “game-changer in several structural, biomedical and energy-harvesting applications.”

Looking at the FDM market currently, we see two general categories of materials: standard polymers (such as PLA and ABS) and polymers reinforced with carbon or glass fibers, also known as composites. The former category has always showcased challenges in terms of layer adhesion and strength of parts, while the latter category—despite demonstrating good strength and stiffness—requires a labour-intensive fabrication process and fiber-reinforced materials are notoriously difficult to recycle. Notably, 3D printing carbon or glass fiber filaments also often requires special, heavy duty hardware.

Finding inspiration from the natural world—specifically spider silk and wood—researchers from ETH Zurich’s Complex Materials group and Soft Materials group developed a method for printing recycled LCPs which resulted in parts with “unprecedented mechanical properties in the deposition direction.” Both spider silk and wood owe many of their mechanical properties to the molecular alignment of proteins along fiber directions.

By mimicking this alignment in the extrusion process and by customizing the local orientation of the 3D printing path according to specific load conditions, the research team demonstrated how its bioinspired approach could offer a solution to 3D printing high performance parts without requiring expensive fiber-reinforced materials.

“Nature provides a rich library of reinforcement designs that have emerged from hundreds of millions of years of evolution,” commented André Studart, head of the Complex Materials group. “3D printing of liquid crystal polymers allows us to implement some of these designs in engineering applications, while also offering recyclability and potentially lower fabrication costs.”

In the research, the ETH Zurich team worked with an Ultimaker 2+ 3D printer equipped with an E3D V6 hotend, which permitted them to print at 295°C. The liquid crystal polymer was also successfully tested using a Prusa MK2 printer and should be compatible with all FDM 3D printers which can reach at least 280°C.

At this stage, the researchers say that parts 3D printed using the recycled LCP material have demonstrated superior strength to parts printed using state-of-the-art 3D printed polymers. Compared to composite parts, LCP components rivalled in terms of quality but benefitted from not needing intensive production steps or processing requirements. Another advantage of the LCP printed parts is that they can be easily recycled.

Moving forward, the team says it is now working to improve the mechanical properties of LCPs even more and is conducting various mechanical tests to understand the system and its potential more clearly. Ultimately, the goal is to bring the technique to market and to collaborate with industry partners to adopt it for real-world applications in the automotive, aerospace and biomedical sectors.