Researchers from State University of New York College of Environmental Science and Forestry, University of Tennessee, Oak Ridge National Laboratory, and The University of Tennessee Institute of Agriculture have come together to research materials for 3D printing, specifically with a focus on composites made from biomass.
Composites are being used more widely as users explore materials that are magnetic, PLA additives, mixtures of recycled polymers, graphene, and more. More natural materials like wood, and specifically lignin, have been a source of experimental studies, too, in efforts to strengthen certain materials for given applications.
In this study, the authors focus on lignocellulosic biomass and derivatives, reviewing and analyzing a variety of additives for 3D printing. Their findings have been released in the recently published ‘3D printing of biomass-derived composites: application and characterization approaches.’
The study of materials is often just a means to an end for the manufacturing of high-performance parts; however, there is also a need for more biocompatible and environmentally-friendly polymers. Because lignocellulosic biomass is natural—and plentiful—it is used in creating bio-fuels, paper, and more, composed of:
- Other extractives
“The development of biomass-derived materials using 3D printing technology as an alternative to fossil oil-based plastics will provide an opportunity to achieve sustainable and renewable bioeconomy,” explained the authors.
Renewable materials have been a substantial source of study, especially in terms of cellulose.
There have been 5,100 patents for 3D printing with cellulose since 2015:
“This trend implies that the application of biomass and its components in 3D printing has become a hot topic and cellulose for 3D printing has been widely used,” stated the authors.
Common methods of 3D printing with composites include fused deposition modeling (FDM), direct-ink writing (DIW), stereolithography (SLA), direct light processing (DLP), and binder jetting.
DIW 3D printing is considered by the authors to be a good candidate for use with cellulose, due to its fluidic properties—meaning that it disperses well in water, acting as a suspension. Hydrogels can be created this way for a variety of bioprinting endeavors, especially due to good rheological properties like shear-thinning, good yield stress for encouraging stability, and both finite elastic modulus and rapid elastic recovery. Previous research recommends CNF hydrogels for use in neural bioprinting, while other additives like chitin (added between the gaps of fibers) may be used in applications like building wind turbine blades. Further crosslinking and ‘enhancing of mechanical performance’ can also result in smart materials, able to respond, and deform to changes in environment like temperature or moisture levels.
In SLA 3D printing, researchers have also been using resin/cellulose blends more often—and especially in medical applications when materials are biocompatible.
“Lignin, the second most abundant terrestrial biopolymer after cellulose, has been under-utilized and, to date, is mostly used for direct combustion,” stated the authors. “Therefore, the valorization of lignin has drawn great attention in the current biorefinery process. Given that lignin contributes to the hydrophobicity, antimicrobial, and antioxidant activities of the plant cell wall, it can be a reinforcing agent in 3D printing composites.”
Lignin offers a range of potential uses, but especially in flame retardant products, anti-aging, and absorption of UV rays. Previous research has also proved its uses for improving tensile performance with better layer adhesion, improvement in drug delivery systems with 3D printed PLA/lignin/tetracycline materials, as well as decreases in warpage and shrinkage. Binder jetting was also used in experimentation with starch-based drug delivery systems.
In contrast to production and uses of cellulose and lignin, whole biomass is simpler to deal with—lacking any requirements for complicated processing, whether physical or chemical. Researchers have created materials for mud-straw walls in construction of basic structures, with wood emerging as ‘one of the most popular biomasses in 3D printing applications.’
As researchers continue to create new wood composites, FDM 3D printing is being used for increased tensile strength, along with other properties; however, experimenting with printing parameters has also been critical in printing materials like PLA with a recycled pine wood additive.
“… understanding the structure of biomass component(s) remains important, along with the utilization of the supramolecular structures, like crystallinity, material anisotropy and interfacial interactions need to be well-studied to help reach the target property of the 3D printed biomass-derived materials,” concluded the authors. “For the processing, various parameters such as the printing resolution and part production rate are the areas that have to undergo further engineering for making 3D printing competitive with conventional material fabrication technologies.
“In the future, the use of compatibilizers and modification of interfacial chemistry may enhance bonding and distribution of biomass-derived fillers with plastics, which could significantly improve the concentration of the fillers with moderate strength to alleviate depletion, at least partially, of the petroleum-based materials. Moreover, characterization techniques that are tailored to the final commercial application can be valuable to better assess the strengths and weaknesses of printed materials. An in-site characterization that has been applied to metal 3D printing is also a possible approach in this field to promote the printing quality.”
What do you think of this news? Let us know your thoughts! Join the discussion of this and other 3D printing topics at 3DPrintBoard.com.[Source / Images: ‘3D printing of biomass-derived composites: application and characterization approaches’]
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