An Intertwined Future: 3D Printing Nanocellulose

Nanocellulose is an exciting new group of materials that could be widely used in manufacturing. Nanocellulose, also called nano cellulose, cellulose nanofibers (CNF), cellulose nanocrystal (CNC), and microfibrillated cellulose (MFC), is a biomaterial. Derived from corn husks, wood pulp, algae, and other materials, it is especially sustainable as it can be made from agricultural waste products. It’s no panacea because it can be energy and water-intensive to produce, but on the whole, it will be more sustainable than many food-source-derived biomaterials.

What is a Fibril?

The cellulose is mechanically broken down into 10 to 100 nanometer fibrils. These rod-like structures can be arranged in a single direction, “woven,” or configured to enable great fatigue strength, deformation, strain, and tensile strengths. They need to be delaminated from the cell walls that contain them, a process that involves chemicals, homogenizers, and many steps to obtain the fibrils. The strength and versatility of these fibrils mean they can strengthen wood, make cellulose cell walls resilient, and give spider silk its incredible properties. Arranging and manipulating their structure can yield very desirable properties. The fibrils themselves reportedly have mechanical strengths between 140–220 GPa, comparable to fibers such as carbon fiber, glass fiber, and other oil-derived fibers. CFRP (carbon fiber reinforced plastics) made with GF, CF, and other fibers are very difficult to recycle. Reinforcing polymers or structures with fibrils would be a very sustainable alternative. Glass and other non-natural fibers are often environmentally challenging to produce, so their displacement would also be beneficial. For 3D printing, these CNC fibrils could be particularly useful.

What is the Nanocellulose Opportunity?

Furthermore, nanocellulose materials could be reconfigurable and tunable, as well as possess shape memory properties. They could be used in filter media, hydrogels, aerogels, 3D printed electronics, bioprinting, coatings, and more. Beyond additive manufacturing, these materials could serve as fillers for bulk plastics, in paper production, and in myriad packaging applications. CNCs are one of those once and future king materials, comparable to RFID, QR codes, PLA for packaging, or technical ceramics. These technical solutions would be viable at scale as technically superior alternatives, if widely adopted. However, their processing currently uses many harmful chemicals and immense amounts of energy. If these challenges are overcome, CNCs and 3D printing could become intertwined, with CNCs becoming the standard reinforcement material for powder bed fusion, vat polymerization, and material extrusion materials. They could also functionalize coatings, improve properties, and provide tunable properties or shape memory properties to parts.

A Sampling of Current Research

In this paper, we learn how properties of “149 ± 2 MPa and a flexural modulus of 15 ± 0.8 GPa” are obtained through controlled drying. By first 3D printing on glass and then on wood while drying in different humidity conditions, they achieve better shape fidelity. A lot of work seems to be focused on substrates, with another paper examining drying and resulting properties from the same perspective. Usually, the material is made for material extrusion and produced as a paste, cross-linked or not. Other researchers are working on making bioinks. In this review paper, hydrogels and inks are explored. One exciting area is using nanocellulose as a material for bone tissue engineering. Another area is wound healing, particularly due to its shape memory properties. Other researchers are conducting similar studies. Shape memory PU is another area powered by CNCs. Another research project investigates shape memory in hydrogels for antibacterial properties. Researchers are also looking at larger scale applications, including architectural ones where shear thinning is exploited to make it a viable material. PLA filament has also been reinforced with nanocellulose, in this case derived from coconut husks. Some very advanced work involves nanocellulose being used for micro supercapacitors using Direct Ink Write. Many different pathways to the final 3D printing material are explored. Firms have tried to commercialize 3D printing materials based on nanocellulose. More broadly, people are considering the material as a kind of universal glue.

Conclusion

I think that nanocellulose is one of the most significant 3D printing-adjacent technological developments. As an environmentally friendly reinforcement material, it could greatly impact the recyclability and environmental friendliness of strong 3D printed components. Using nanocellulose instead of CF or GF for reinforcement could significantly support our growth. Additionally, the potential for shape memory and tunable properties presents another major opportunity. This advancement could open a new arena for dialing in, devising, and executing the right properties for parts. Coupled with its shape memory properties, nanocellulose is something that should be closely examined by anyone active in polymer 3D printing.