3D Printing Real Wood With Just Cellulose and Lignin

The quest to create 3D-printed wood using cellulose and lignin ink has seen significant progress with a recent study published in Science Advances by MD Shajedul Hoque Thakur and colleagues. Employing direct ink writing (DIW) as the additive manufacturing method, the researchers have developed a water-based ink with a composition of TOCN (tempo-oxidized cellulose nanofiber), aqueous CNC (cellulose nanocrystals), and lignin. This ink, with a viscosity akin to clay, aims to replicate the structural elements of natural wood, including both crystalline and amorphous cellulose components.

The ink is extruded through a syringe head installed in a Hyrel 3D Engine HR 3D printer, similar to an FDM printer but tailored for bioprinting and laboratory use. The printed shapes undergo post-printing operations, including freeze drying or additional heating (at 180°C), and some samples are subjected to hot pressing. These processes help enhance the binding of lignin and improve the durability of the printed structures.

Comparative analysis with natural hardwood (balsa wood) reveals promising results, showcasing properties similar to those found in natural wood. The heating and pressure applied during post-printing operations promote annealing between layers, mimicking the growth patterns observed in wood. However, the printed wood lacks the long fibers characteristic of natural wood growth, indicating areas for further refinement.

While the current process involves energy-intensive and cumbersome steps, the study underscores the potential for advancements in ink formulation and post-processing methods to enhance accessibility and efficiency. With continued development, DIW wood printing could become a staple in hobbyist workshops and manufacturing facilities, akin to established 3D printing techniques like FDM, SLS, and SLA.

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