Mapping 3D Printability of Ionically Cross-Linked Cellulose Nanocrystal Inks: Architecting from Nano- to Macroscale Structures

Abstract

Engineering the rheological properties of colloidal inks is one of the main challenges in achieving high-fidelity 3D printing. Herein, we provide a comprehensive study on the rheological behavior of inks based on cellulose nanocrystals (CNCs) in the presence of given salts to enable high-quality 3D printing. The rheological properties of the CNC suspensions are tailored by considering the nature of the electrolyte (i.e., 10 types of salts featuring different ion sizes, charge numbers, and inter-and intra-molecular interactions) at various concentrations (25−100 mM). A high printing fidelity is achieved in a narrow CNC and salt concentration range, significantly depending on the salt type. The structure−property relationship is explored in a "3D-printing" space (2D map), introducing a guideline for researchers active in this field. To further unravel the effect of salt type on morphological properties, CNC aerogels are developed by freeze-drying the printed structures. The results illustrate that enhancing viscoelastic properties render a denser structure featuring smaller pores.

Crystalline and Hairy Nanocelluloses for 3D Printed Hydrogels and Strongly Structured Cryogels

“…CNC particles are placed closely together at this concentration. We have also carried out a comprehensive study on the optimization of CNC concentration in the presence of 10 different salts for high-fidelity 3D printing . According to these results, the highest G ′ and G ″ values can be achieved for CNC suspensions containing NaHCO 3 compared to other salts.…”

“…By plotting storage and loss moduli versus shear stress (stress amplitude test), the yield stress (τ y ), where both G ″ and G ′ are equal, could be estimated for all samples. The yield stress determined in this way is equivalent to the yield stress derived from a stress–strain curve …”

“…Here, we evaluated the mechanical features of the samples under compressive deformation (Figure ). The compression curves for porous materials usually show two distinct regions: a small-strain region with collapsing walls and a large-strain region with the pore cell walls in contact with opposite-facing walls.…”

“…The yield stress determined in this way is equivalent to the yield stress derived from a stress− strain curve. 29 According to Figure 4b, the obtained τ y values for CNC/ ENCC (1:2), CNC/ENCC (1:1), CNC/ENCC (2:1), and CNC (10 wt %) were 16, 133, 145, and 1016 Pa, respectively (derived from the stress where the modulus suddenly approaches zero). A hybrid hydrogel with high yield stress generally produces a stiffer construct.…”

3D printing of solvent-treated PEDOT:PSS inks for electromagnetic interference shielding

“…[36][37][38] Intense shear-thinning behavior conjugated with high yield stress bestows inks with uid-like behavior during printing and a solid-like behavior immediately aer printing. 37,39 Recently, it has been shown that inks containing 7 wt% PEDOT:PSS possess proper rheological properties for high delity 3D printing of implantable conductive patches. 33 Further to that, it was shown that the addition of 2D MXenes nanosheets to PEDOT:PSS inks contributes to improving their rheological properties, leading to high-resolution printed lines.…”