3D printing with cellulose nanofibrils enabled by microwave irradiation

Abstract

Cellulose nanofibrils (CNFs) offer a sustainable alternative for 3D printing applications when compared to petroleum-based polymers. However, the significant amount of water in CNF suspension limits their application due to the need for lengthy and energy-intensive drying technologies. This study presents a novel process for the 3D printing of CNFs using urea and carboxymethyl cellulose (CMC) as additives enabled by microwave irradiation. Additionally, this process eliminates the need for freeze-drying or conventional oven drying methods. Two multilayer geometries were constructed: octagonal shells and cuboids with 100% infill. The 3D-printed paste was first solidified by freezing followed by immediate thawing through microwave irradiation. The amplitude-sweep and zeta potential analyses revealed information on the effect of urea and CMC on the printability of CNFs. The compressive testing results indicated that structures containing 2 pph (Parts per hundred) CMC exhibited higher compressive strength than the structures with 1 pph CMC, regardless of the urea concentration. Additionally, the high CMC content enhanced the interfacial adhesion between the layers. In addition, a thorough investigation of the chemical interactions among CNF, urea, and CMC was conducted using Fourier-transform infrared spectroscopy (FTIR). This distinct approach for 3D printing, based on the use of CNFs and microwave irradiation, provides an economically viable option to promote sustainable nanomaterials in the field of additive manufacturing and paves the way for further development.