Article
A Novel Additive Manufacturing Method of Cellulose Gel
Hossein Najaf Zadeh
1,2,
* , Daniel Bowles
1
, Tim Huber
2,3
and Don Clucas
1
Citation: Najaf Zadeh, H.; Bowles,
D.; Huber, T.; Clucas, D. A Novel
Additive Manufacturing Method of
Cellulose Gel. Materials 2021, 14, 6988.
https://doi.org/10.3390/ma14226988
Academic Editor: Ludwig Cardon
Received: 23 September 2021
Accepted: 12 November 2021
Published: 18 November 2021
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1
College of Engineering, University of Canterbury, Private Bag 4800, Christchurch 8020, New Zealand;
djb252@uclive.ac.nz (D.B.); don.clucas@canterbury.ac.nz (D.C.)
2
Biomolecular Interaction Centre, University of Canterbury, Private Bag 4800,
Christchurch 8020, New Zealand; Tim.huber@canterbury.ac.nz
3
School of Product Design, University of Canterbury, Private Bag 4800, Christchurch 8020, New Zealand
* Correspondence: hossein.najafzadeh@canterbury.ac.nz
Abstract:
Screen-additive manufacturing (SAM) is a potential method for producing small intricate
parts without waste generation, offering minimal production cost. A wide range of materials,
including gels, can be shaped using this method. A gel material is composed of a three-dimensional
cross-linked polymer or colloidal network immersed in a fluid, known as hydrogel when its main
constituent fluid is water. Hydrogels are capable of absorbing and retaining large amounts of water.
Cellulose gel is among the materials that can form hydrogels and, as shown in this work, has the
required properties to be directly SAM, including shear thinning and formation of post-shearing gel
structure. In this study, we present the developed method of SAM for the fabrication of complex-
shaped cellulose gel and examine whether successive printing layers can be completed without
delamination. In addition, we evaluated cellulose SAM without the need for support material. Design
of Experiments (DoE) was applied to optimize the SAM settings for printing the novel cellulose-based
gel structure. The optimum print settings were then used to print a periodic structure with micro
features and without the need for support material.
Keywords:
additive manufacturing; cellulose; gel; hydrogel; screen printing; 3D printing; screen
additive manufacturing; stencil additive manufacturing
1. Introduction
In recent years, various approaches based on additive manufacturing (AM), popularly
known as 3D printing, of natural materials or biopolymers have been explored to fabricate
complex geometries of gels [1–4]. Although 3D printing technology offers great potential,
there exists significant challenges to overcome the limited capabilities of the 3D printing
gels, such as part resolution, processing and printing speed, and the lack of diversity in 3D
printable biomaterials. One of the classes of materials that has a wide range of applications
in bio-engineering is hydrogels [
5
]. They are highly hydrophilic polymer networks of
natural or synthetic origin that are strong enough to absorb and retain a large amount
of water.
Polysaccharides are one of the materials that can be turned into hydrogels; the most
common being cellulose, chitosan, and agarose. Cellulose, as the most abundant organic
compound on Earth, has desirable mechanical and chemical characteristics, including
permeability, nontoxicity, biocompatibility, and biodegradability [
6
]. Moreover, it is an
inexpensive and environmentally friendly material. Fabricating hydrogels out of cellulose
makes it favorable for many applications, including tissue engineering [
7
], cell culture [
8
],
drug delivery [
9
], purification [
10
], and agrochemicals [
11
]. Cellulose is neither soluble
nor meltable; however, it can be dissolved in a few classes of solvents, such as ionic liquid
1-ethyl-3-methylimidazolium acetate [
12
], N-methylmorpholine-N-oxide (NMMO) [
13
],
and, the most recently developed, a non-hazardous aqueous solvent of NaOH/urea [
14
].
Dissolved cellulose in NaOH/urea solvent can form an irreversible gel by the heating or
cooling of the solution [15].
Materials 2021, 14, 6988. https://doi.org/10.3390/ma14226988 https://www.mdpi.com/journal/materials
