3D-Printable Nanocellulose-Based Functional Materials: Fundamentals and Applications

Abstract

Nanomaterials obtained from sustainable and natural sources have seen tremendous growth in recent times due to increasing interest in utilizing readily and widely available resources. Nanocellulose materials extracted from renewable biomasses hold great promise for increasing the sustainability of conventional materials in various applications owing to their biocompatibility, mechanical properties, ease of functionalization, and high abundance. Nanocellulose can be used to reinforce mechanical strength, impart antimicrobial activity, provide lighter, biodegradable, and more robust materials for packaging, and produce photochromic and electrochromic devices. While the fabrication and properties of nanocellulose are generally well established, their implementation in novel products and applications requires surface modification, assembly, and manufacturability to enable rapid tooling and scalable production. Additive manufacturing techniques such as 3D printing can improve functionality and enhance the ability to customize products while reducing fabrication time and wastage of materials. This review article provides an overview of nanocellulose as a sustainable material, covering the different properties, preparation methods, printability and strategies to functionalize nanocellulose into 3D-printed constructs. The applications of 3D-printed nanocellulose composites in food, environmental, and energy devices are outlined, and an overview of challenges and opportunities is provided.

Keywords: 3D printing; additive manufacturing; composites; nanocellulose; packaging; sustainable materials.

Figure 1

Schematic diagram of nanocellulose: source, processing, and 3D printability.

Figure 2

Graphs showing the number of publications between 2011–2021 (a) and publications per country (b) using Web of Science (accessed on 30 June 2021).

Figure 3

A queen chess piece printed with pure CNFs which collapsed due to lack of crosslinking (a), poor printability shown by unsuccessful grid printed with pure XT (b). Three-dimensional printed and crosslinked, freestanding and crosslinked cylinder (c) grid, handled and bent in air (d). Rook chess piece, held upside down from optimized formulation of CNF and XT (e), reprinted with permission from ref. [49]. Copyright 2017, American Chemical Society.

Figure 4

Illustration of the steps involved in the preparation of 3D-printed functional CNC-based hydrogels, involving: (A) ink formulation, (B) ink writing of cellulose-based polymer ink, (C) post-treatment to cure the printed construct, and (D) (i–v) characteristics of inks and printed constructs, reprinted from ref. [53].

Figure 5

Illustration of CNC acetylation process and 3D-printed nanocellulose–PHBH-based composites showing the (A) acetylation process (a) of a CNC particle of a cellulose structure (b) by sulphuric acid (c) and acetic anhydride (d), and acetylated nanocellulose after functionalization (e–g). (B) FDM 3D-printed nanocellulose composites of PHBH-acetylated CNC (10%) showing an alteration of 0–90° (a–c) as an example of a medical device for finger dislocation (c,d), used with permission from ref. [54].

Figure 6

Summary highlighting the broad examples of applications of 3D-printed nanocellulose constructs.

Figure 7

Calibration curves of tested samples (green, without plasticizer, and blue, with plasticizer) (a); RH sensors based on CNF films with screen-printed carbon electrodes (b). Impedance spectra under different humidity levels for the sample with plasticizer (c) and without plasticizer (d) at 25  °C. Insets: spectra for humidity levels 50, 60, 70, 80, and 90%, used with permission from ref. [53].

Figure 8

Three-dimensional-printed tensile specimen of PLA (a) and PLA/1CNF (b) composites, scanning electron microscopy micrographs (×600 magnification) of the tensile fractured surface of compression-molded PLA (c), PLA/1% CNF (d), PLA/3CNF (e), and PLA/5CNF (f) composites, used with permission from ref. [59].

Figure 9

Tensile stress–strain curve of compression-molded and 3D-printed PLA and PLA/CNF composites (a) and histograms of mechanical properties of the samples (b,c). Scanning electron microscopy micrographs (×150 and ×600) of the tensile fracture surface of 3D-printed PLA (d,e) and 3D-PLA/1% cellulose nanofiber composites (f,g), used with permission from ref. [59].

Figure 10

The material extrusion type of device used for 3D printing of food materials (a). The effect of the oven freeze-drying on the appearance of 3D-printed samples (b): 0.8% CNF + 50% SSMP (1) and 60% SSMP (2), used with permission from ref. [65].

Figure 11

SEM images of CMC before (1a) and after freeze-drying (1b). Viscosity as a function of the shear rate for CMC and CMC-based inks (1c), G′ and G″ as a function of the shear stress for CMC and CMC-based inks (1d); Photographs of CMC-based 3D-printed aerogel before curing (2a), after curing (2b) and after freeze-drying (2c), used with permission from Ref. [50].

Figure 12

Morphology of 3D-printed samples by 75ink with different crosslinking times, before (a) and after (b) UV curing and after freeze-drying (c1,c2). (d) Stress-strain curves, (e) cushioning curves, and (f) thrice compression resilience ratio of samples with different crosslinking times, used with permission from ref. [50].

Figure 13

Design of CNF-based smart freshness indicator prepared by a 2,2,6,6-tetramethyl piperidinyl-1-oxyl (TEMPO) catalysis method for monitoring degradation in packaged meat, used with permission from ref. [44].

Figure 14

Optical photographs (a–d) and SEM images (e–h) of films obtained with low-viscosity inks (a,b,e,f) and high-viscosity pastes (c,d,g,h). Scale bars (in white) = 1 mm (a,b), 400 µm (c,d), 100 µm (e,g), and 50 µm (f,h). Each image (either optical or from SEM) corresponds to a random point of each sample, none is the direct magnification of another. Used with permission from ref. [70].

Figure 15

Three-dimensional scatter plot describing the effect of CNTs added in basic pH and conditions to obtain liquid inks (blue), viscous pastes (orange), and self-standing hydrogels (gray) (a). All samples had basic pH. Photographs of films made from low-viscosity inks (b) and high-viscosity pastes (c) on glass substrates. Real images of a hydrogel derived from hydrothermal treatment in water (left) and preparation scheme of aerogels by unidirectional freezing followed by lyophilization (right) (d), used with permission from ref. [70].