Complex‐Shaped Cellulose Composites Made by Wet Densification of 3D Printed Scaffolds

Abstract

Cellulose is an attractive material resource for the fabrication of sustainable functional products, but its processing into structures with complex architecture and high cellulose content remains challenging. Such limitation has prevented cellulose‐based synthetic materials from reaching the level of structural control and mechanical properties observed in their biological counterparts, such as wood and plant tissues. To address this issue, a simple approach is reported to manufacture complex‐shaped cellulose‐based composites, in which the shaping capabilities of 3D printing technologies are combined with a wet densification process that increases the concentration of cellulose in the final printed material. Densification is achieved by exchanging the liquid of the wet printed material with a poor solvent mixture that induces attractive interactions between cellulose particles. The effect of the solvent mixture on the final cellulose concentration is rationalized using solubility parameters that quantify the attractive interparticle interactions. Using X‐ray diffraction analysis and mechanical tests, 3D printed composites obtained through this process are shown to exhibit highly aligned microstructures and mechanical properties significantly higher than those obtained by earlier additively manufactured cellulose‐based materials. These features enable the fabrication of cellulose‐rich synthetic structures that more closely resemble the exquisite designs found in biological materials grown by plants in nature.

Functional Materials from Nanocellulose: Utilizing Structure–Property Relationships in Bottom‐Up Fabrication

“…[ 253–256 ] Hausmann et al demonstrated the wet densification of 3D‐printed CNC/CNF composite scaffolds via their submersion in differing solvents and subsequent polymerization of monomer species present in the solvent bath. [ 257 ] By varying the CNC/CNF ink ratio along with the filament orientation with respect to the applied stress, scaffolds with drastically different mechanical properties could be achieved. Wang et al demonstrated that surface modification of CNCs with photoinitiating bis(acyl)phosphane oxide groups enabled the polymerization of monofunctional methacrylate moieties during 3D printing, resulting in scaffolds with good shape persistence and improved mechanical properties.…”

Surface and Interface Engineering for Nanocellulosic Advanced Materials

“…The nanocomposites exhibited highly aligned microstructures and high mechanical properties, and allowed fabrication of nanocomposites with 3D complex shapes. [ 160 ]…”

Wood and the Activity of Dead Tissue

“…Recently, 3D‐printed cellulose‐containing scaffolds were wet densified, resulting in composites with highly aligned cellulose and a volume fraction of more than 27% cellulose. [ 93 ] This is a promising direction toward the designed assembly of cellulose for structural materials requiring good mechanical properties. The printing of materials with anisotropic composition is also of interest for 3D wood printing.…”