2, ETH Zürich, Dubendorf, , Switzerland
Cellulose nanocrystal (CNC) is a bio-based and renewable material extracted from wood and algae or produced by bacteria. The alignment of CNCs is crucial for direction specific enhanced mechanical properties in composite applications. We utilize direct-ink writing (DWI) to assemble complex cellulose-based geometries with controlled orientation and spatial distribution of nanocrystals within the printed structure. Using polarized imaging rheology we correlate the dynamic flow behavior of CNC-based inks with the quality of nanocrystal alignment occurring during 3D printing. In order to control the quality of alignment during the 3D printing process, the printing pressure and the viscoelastic properties of the material have to be well characterized. After printing, the resulting part and its mechanical properties are determined in order to create composites with well-defined properties. By understanding the effect of the concentration of reinforcing nanocrystals on the rheological properties of the ink during the printing process, 3D objects with improved printability and mechanical properties were obtained. Our findings pave the way towards the fabrication of high-performance materials with renewable resources using a cost-effective additive manufacturing technique.