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NextGen Materials for 3D Printing

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A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Manufacturing Processes and Systems".

Deadline for manuscript submissions: closed (31 December 2017) | Viewed by 142931

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Prof. Dr. Chee Kai Chua

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Singapore Centre for 3D Printing, School of Mechanical & Aerospace Engineering, Nanyang Technological University, N3.1-B2c-03b, 50 Nanyang Avenue, Singapore 639798, Singapore
Interests: geometric modelling; rapid prototyping; additive manufacturing; 3D printing; reverse engineering; biomedical engineering design; tissue engineering; biomaterials; bioprinting
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Dr. Jia An

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Singapore Centre for 3D Printing, School of Mechanical & Aerospace Engineering, Nanyang Technological University, N3.1-B2c-03b, 50 Nanyang Avenue, Singapore 639798, Singapore
Interests: 3D printing; bioprinting; biomaterials; polymer processing; polymer microfibers; polymer membranes; tissue engineering
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Prof. Dr. Wai Yee Yeong

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Guest Editor

Singapore Centre for 3D Printing, School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798, Singapore
Interests: additive manufacturing; 3D printing; 3D bioprinting
Special Issues, Collections and Topics in MDPI journals

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Dear Colleagues,

3D printing, formally known as additive manufacturing, has advanced significantly in the field of processing materials. Recently, many materials, most deemed as non-printable before, have surfaced in the field of 3D printing as new 3D printable materials; for example, glass, concrete, carbon fibers, dissolvable metals, etc. Though not many have reached commercial maturity, the endless possibilities of 3D printing have been undoubtedly manifested. This causes us to consider, by looking at today’s range of materials and the range of 3D printable materials, what will 3D printing look like tomorrow? This exciting question motivates us to propose a Special Issue on the next generation of 3D printing materials.

The focus of this Special Issue is on new, 3D printable materials. Any topics involving 3D printing materials will be of interest to us. Please refer to the following list of suggested keywords for the scope of this Special Issue. We look forward to your contribution.

Prof. Dr. Chee Kai Chua
Assist. Prof. Dr. Wai Yee Yeong
Dr. Jia An
Guest Editors

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

Multi-materials
Hybrid materials
Smart materials (e.g. shape memory materials)
Magnetic materials
Glass and ceramics
Functional materials
New biomaterials
Nanomaterials/Nanocomposites
Cement and concrete
Carbon fibre composites
Dissolvable metals
Drugs/pharmaceuticals
Food/nutrients

Published Papers (13 papers)

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Editorial

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2 pages, 185 KiB

Open AccessEditorial

Special Issue: NextGen Materials for 3D Printing

by Chee Kai Chua, Wai Yee Yeong and Jia An

Materials 2018, 11(4), 555; https://doi.org/10.3390/ma11040555 - 04 Apr 2018

Cited by 5 | Viewed by 4663

Abstract

Only a handful of materials are well-established in three-dimensional (3D) printing and well-accepted in industrial manufacturing applications. However, recent advances in 3D printable materials have shown potential for enabling numerous novel applications in the future. This special issue, consisting of 2 reviews and [...] Read more.

(This article belongs to the Special Issue NextGen Materials for 3D Printing)

Research

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22 pages, 20226 KiB

Open AccessArticle

3D Printability of Alginate-Carboxymethyl Cellulose Hydrogel

by Ahasan Habib, Venkatachalem Sathish, Sanku Mallik and Bashir Khoda

Materials 2018, 11(3), 454; https://doi.org/10.3390/ma11030454 - 20 Mar 2018

Cited by 202 | Viewed by 18034

Abstract

Three-dimensional (3D) bio-printing is a revolutionary technology to reproduce a 3D functional living tissue scaffold in-vitro through controlled layer-by-layer deposition of biomaterials along with high precision positioning of cells. Due to its bio-compatibility, natural hydrogels are commonly considered as the scaffold material. However, the mechanical integrity of a hydrogel material, especially in 3D scaffold architecture, is an issue. In this research, a novel hybrid hydrogel, that is, sodium alginate with carboxymethyl cellulose (CMC) is developed and systematic quantitative characterization tests are conducted to validate its printability, shape fidelity and cell viability. The outcome of the rheological and mechanical test, filament collapse and fusion test demonstrate the favorable shape fidelity. Three-dimensional scaffold structures are fabricated with the pancreatic cancer cell, BxPC3 and the 86% cell viability is recorded after 23 days. This hybrid hydrogel can be a potential biomaterial in 3D bioprinting process and the outlined characterization techniques open an avenue directing reproducible printability and shape fidelity. Full article

(This article belongs to the Special Issue NextGen Materials for 3D Printing)

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27 pages, 18046 KiB

Open AccessArticle

Design and 4D Printing of Cross-Folded Origami Structures: A Preliminary Investigation

by Joanne Ee Mei Teoh, Jia An, Xiaofan Feng, Yue Zhao, Chee Kai Chua and Yong Liu

Materials 2018, 11(3), 376; https://doi.org/10.3390/ma11030376 - 03 Mar 2018

Cited by 40 | Viewed by 6950

Abstract

In 4D printing research, different types of complex structure folding and unfolding have been investigated. However, research on cross-folding of origami structures (defined as a folding structure with at least two overlapping folds) has not been reported. This research focuses on the investigation of cross-folding structures using multi-material components along different axes and different horizontal hinge thickness with single homogeneous material. Tensile tests were conducted to determine the impact of multi-material components and horizontal hinge thickness. In the case of multi-material structures, the hybrid material composition has a significant impact on the overall maximum strain and Young’s modulus properties. In the case of single material structures, the shape recovery speed is inversely proportional to the horizontal hinge thickness, while the flexural or bending strength is proportional to the horizontal hinge thickness. A hinge with a thickness of 0.5 mm could be folded three times prior to fracture whilst a hinge with a thickness of 0.3 mm could be folded only once prior to fracture. A hinge with a thickness of 0.1 mm could not even be folded without cracking. The introduction of a physical hole in the center of the folding/unfolding line provided stress relief and prevented fracture. A complex flower petal shape was used to successfully demonstrate the implementation of overlapping and non-overlapping folding lines using both single material segments and multi-material segments. Design guidelines for establishing cross-folding structures using multi-material components along different axes and different horizontal hinge thicknesses with single or homogeneous material were established. These guidelines can be used to design and implement complex origami structures with overlapping and non-overlapping folding lines. Combined overlapping folding structures could be implemented and allocating specific hole locations in the overall designs could be further explored. In addition, creating a more precise prediction by investigating sets of in between hinge thicknesses and comparing the folding times before fracture, will be the subject of future work. Full article

(This article belongs to the Special Issue NextGen Materials for 3D Printing)

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12 pages, 3371 KiB

Open AccessArticle

A 3D-Printable Polymer-Metal Soft-Magnetic Functional Composite—Development and Characterization

by Bilal Khatri, Karl Lappe, Dorit Noetzel, Kilian Pursche and Thomas Hanemann

Materials 2018, 11(2), 189; https://doi.org/10.3390/ma11020189 - 25 Jan 2018

Cited by 86 | Viewed by 9530

Abstract

In this work, a 3D printed polymer–metal soft-magnetic composite was developed and characterized for its material, structural, and functional properties. The material comprises acrylonitrile butadiene styrene (ABS) as the polymer matrix, with up to 40 vol. % stainless steel micropowder as the filler. The composites were rheologically analyzed and 3D printed into tensile and flexural test specimens using a commercial desktop 3D printer. Mechanical characterization revealed a linearly decreasing trend of the ultimate tensile strength (UTS) and a sharp decrease in Young’s modulus with increasing filler content. Four-point bending analysis showed a decrease of up to 70% in the flexural strength of the composite and up to a two-factor increase in the secant modulus of elasticity. Magnetic hysteresis characterization revealed retentivities of up to 15.6 mT and coercive forces of up to 4.31 kA/m at an applied magnetic field of 485 kA/m. The composite shows promise as a material for the additive manufacturing of passive magnetic sensors and/or actuators. Full article

(This article belongs to the Special Issue NextGen Materials for 3D Printing)

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13 pages, 4414 KiB

Open AccessArticle

Polymer-Ceramic Composite Scaffolds: The Effect of Hydroxyapatite and β-tri-Calcium Phosphate

by Boyang Huang, Guilherme Caetano, Cian Vyas, Jonny James Blaker, Carl Diver and Paulo Bártolo

Materials 2018, 11(1), 129; https://doi.org/10.3390/ma11010129 - 14 Jan 2018

Cited by 136 | Viewed by 9318

Abstract

The design of bioactive scaffolds with improved mechanical and biological properties is an important topic of research. This paper investigates the use of polymer-ceramic composite scaffolds for bone tissue engineering. Different ceramic materials (hydroxyapatite (HA) and β-tri-calcium phosphate (TCP)) were mixed with poly-ε-caprolactone (PCL). Scaffolds with different material compositions were produced using an extrusion-based additive manufacturing system. The produced scaffolds were physically and chemically assessed, considering mechanical, wettability, scanning electron microscopy and thermal gravimetric tests. Cell viability, attachment and proliferation tests were performed using human adipose derived stem cells (hADSCs). Results show that scaffolds containing HA present better biological properties and TCP scaffolds present improved mechanical properties. It was also possible to observe that the addition of ceramic particles had no effect on the wettability of the scaffolds. Full article

(This article belongs to the Special Issue NextGen Materials for 3D Printing)

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12 pages, 4599 KiB

Open AccessArticle

Effects of T2 Heat Treatment on Microstructure and Properties of the Selective Laser Melted Aluminum Alloy Samples

by Lianfeng Wang, Jing Sun, Xiaogang Zhu, Lingyu Cheng, Yun Shi, Lijie Guo and Biao Yan

Materials 2018, 11(1), 66; https://doi.org/10.3390/ma11010066 - 03 Jan 2018

Cited by 21 | Viewed by 4626

Abstract

In this paper, aluminum alloy samples were fabricated by selective laser melting (SLM) and subsequently T2 heat treatment was undertaken. In order to obtain comprehensive results, various experiments on densification, hardness, tensile strength, bending strength and microstructure characterization were carried out. The results show that densification of samples after T2 heat treatment does not vary very much from the SLMed ones, while the Brinell hardness and strength decreases to about 50%. Moreover, the plasticity and fracture deflection increases about 3 fold. The effects on the microstructure and the mechanical properties of the SLMed aluminum alloy samples and subsequent T2 heat treatment were studied. Full article

(This article belongs to the Special Issue NextGen Materials for 3D Printing)

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3703 KiB

Open AccessArticle

Visible Light Photoinitiator for 3D-Printing of Tough Methacrylate Resins

by Bernhard Steyrer, Philipp Neubauer, Robert Liska and Jürgen Stampfl

Materials 2017, 10(12), 1445; https://doi.org/10.3390/ma10121445 - 19 Dec 2017

Cited by 97 | Viewed by 11761

Abstract

Lithography-based additive manufacturing was introduced in the 1980s, and is still the method of choice for printing accurate plastic parts with high surface quality. Recent progress in this field has made tough photopolymer resins and cheap LED light engines available. This study presents the influence of photoinitiator selection and post-processing on the thermomechanical properties of various tough photopolymers. The influence of three photoinitiators (Ivocerin, BAPO, and TPO-L) on the double-bond conversion and mechanical properties was investigated by mid infrared spectroscopy, dynamic mechanical analysis and tensile tests. It was found that 1.18 wt % TPO-L would provide the best overall results in terms of double-bond conversion and mechanical properties. A correlation between double-bond conversion, yield strength, and glass transition temperature was found. Elongation at break remained high after post-curing at about 80–100%, and was not influenced by higher photoinitiator concentration. Finally, functional parts with 41 MPa tensile strength, 82% elongation at break, and 112 °C glass transition temperature were printed on a 405 nm DLP (digital light processing) printer. Full article

(This article belongs to the Special Issue NextGen Materials for 3D Printing)

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70685 KiB

Open AccessArticle

Ceramic-Based 4D Components: Additive Manufacturing (AM) of Ceramic-Based Functionally Graded Materials (FGM) by Thermoplastic 3D Printing (T3DP)

by Uwe Scheithauer, Steven Weingarten, Robert Johne, Eric Schwarzer, Johannes Abel, Hans-Jürgen Richter, Tassilo Moritz and Alexander Michaelis

Materials 2017, 10(12), 1368; https://doi.org/10.3390/ma10121368 - 28 Nov 2017

Cited by 67 | Viewed by 11509

Abstract

In our study, we investigated the additive manufacturing (AM) of ceramic-based functionally graded materials (FGM) by the direct AM technology thermoplastic 3D printing (T3DP). Zirconia components with varying microstructures were additively manufactured by using thermoplastic suspensions with different contents of pore-forming agents (PFA), which were co-sintered defect-free. Different materials were investigated concerning their suitability as PFA for the T3DP process. Diverse zirconia-based suspensions were prepared and used for the AM of single- and multi-material test components. All of the samples were sintered defect-free, and in the end, we could realize a brick wall-like component consisting of dense (<1% porosity) and porous (approx. 5% porosity) zirconia areas to combine different properties in one component. T3DP opens the door to the AM of further ceramic-based 4D components, such as multi-color, multi-material, or especially, multi-functional components. Full article

(This article belongs to the Special Issue NextGen Materials for 3D Printing)

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6956 KiB

Open AccessFeature PaperArticle

Experimental Exploration of Metal Cable as Reinforcement in 3D Printed Concrete

by Freek P. Bos, Zeeshan Y. Ahmed, Evgeniy R. Jutinov and Theo A. M. Salet

Materials 2017, 10(11), 1314; https://doi.org/10.3390/ma10111314 - 16 Nov 2017

Cited by 176 | Viewed by 12713

Abstract

The Material Deposition Method (MDM) is enjoying increasing attention as an additive method to create concrete mortar structures characterised by a high degree of form-freedom, a lack of geometrical repetition, and automated construction. Several small-scale structures have been realised around the world, or are under preparation. However, the nature of this construction method is unsuitable for conventional reinforcement methods to achieve ductile failure behaviour. Sometimes, this is solved by combining printing with conventional casting and reinforcing techniques. This study, however, explores an alternative strategy, namely to directly entrain a metal cable in the concrete filament during printing to serve as reinforcement. A device is introduced to apply the reinforcement. Several options for online reinforcement media are compared for printability. Considerations specific to the manufacturing process are discussed. Subsequently, pull-out tests on cast and printed specimens provide an initial characterisation of bond behaviour. Bending tests furthermore show the potential of this reinforcement method. The bond stress of cables in printed concrete was comparable to values reported for smooth rebar but lower than that of the same cables in cast concrete. The scatter in experimental results was high. When sufficient bond length is available, ductile failure behaviour for tension parallel to the filament direction can be achieved, even though cable slip occurs. Further improvements to the process should pave the way to achieve better post-crack resistance, as the concept in itself is feasible. Full article

(This article belongs to the Special Issue NextGen Materials for 3D Printing)

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9263 KiB

Open AccessFeature PaperArticle

Selective Laser Sintering of Porous Silica Enabled by Carbon Additive

by Shuai Chang, Liqun Li, Li Lu and Jerry Ying Hsi Fuh

Materials 2017, 10(11), 1313; https://doi.org/10.3390/ma10111313 - 16 Nov 2017

Cited by 27 | Viewed by 11799

Abstract

The aim of this study is to investigate the possibility of a freeform fabrication of porous ceramic parts through selective laser sintering (SLS). SLS was proposed to manufacture ceramic green parts because this additive manufacturing technique can be used to fabricate three-dimensional objects directly without a mold, and the technique has the capability of generating porous ceramics with controlled porosity. However, ceramic printing has not yet fully achieved its 3D fabrication capabilities without using polymer binder. Except for the limitations of high melting point, brittleness, and low thermal shock resistance from ceramic material properties, the key obstacle lies in the very poor absorptivity of oxide ceramics to fiber laser, which is widely installed in commercial SLS equipment. An alternative solution to overcome the poor laser absorptivity via improving material compositions is presented in this study. The positive effect of carbon additive on the absorptivity of silica powder to fiber laser is discussed. To investigate the capabilities of the SLS process, 3D porous silica structures were successfully prepared and characterized. Full article

(This article belongs to the Special Issue NextGen Materials for 3D Printing)

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Review

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12 pages, 6805 KiB

Open AccessReview

A Review of Selective Laser Melted NiTi Shape Memory Alloy

by Zhong Xun Khoo, Yong Liu, Jia An, Chee Kai Chua, Yu Fang Shen and Che Nan Kuo

Materials 2018, 11(4), 519; https://doi.org/10.3390/ma11040519 - 29 Mar 2018

Cited by 108 | Viewed by 8974

Abstract

NiTi shape memory alloys (SMAs) have the best combination of properties among the different SMAs. However, the limitations of conventional manufacturing processes and the poor manufacturability of NiTi have critically limited its full potential applicability. Thus, additive manufacturing, commonly known as 3D printing, has the potential to be a solution in fabricating complex NiTi smart structures. Recently, a number of studies on Selective Laser Melting (SLM) of NiTi were conducted to explore the various aspects of SLM-produced NiTi. Compared to producing conventional metals through the SLM process, the fabrication of NiTi SMA is much more challenging. Not only do the produced parts require a high density that leads to good mechanical properties, strict composition control is needed as well for the SLM NiTi to possess suitable phase transformation characteristics. Additionally, obtaining a good shape memory effect from the SLM NiTi samples is another challenging task that requires further understanding. This paper presents the results of the effects of energy density and SLM process parameters on the properties of SLM NiTi. Its shape memory properties and potential applications were then reviewed and discussed. Full article

(This article belongs to the Special Issue NextGen Materials for 3D Printing)

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19 pages, 3625 KiB

Open AccessFeature PaperReview

Advanced Material Strategies for Next-Generation Additive Manufacturing

by Jinke Chang, Jiankang He, Mao Mao, Wenxing Zhou, Qi Lei, Xiao Li, Dichen Li, Chee-Kai Chua and Xin Zhao

Materials 2018, 11(1), 166; https://doi.org/10.3390/ma11010166 - 22 Jan 2018

Cited by 78 | Viewed by 13776

Abstract

Additive manufacturing (AM) has drawn tremendous attention in various fields. In recent years, great efforts have been made to develop novel additive manufacturing processes such as micro-/nano-scale 3D printing, bioprinting, and 4D printing for the fabrication of complex 3D structures with high resolution, living components, and multimaterials. The development of advanced functional materials is important for the implementation of these novel additive manufacturing processes. Here, a state-of-the-art review on advanced material strategies for novel additive manufacturing processes is provided, mainly including conductive materials, biomaterials, and smart materials. The advantages, limitations, and future perspectives of these materials for additive manufacturing are discussed. It is believed that the innovations of material strategies in parallel with the evolution of additive manufacturing processes will provide numerous possibilities for the fabrication of complex smart constructs with multiple functions, which will significantly widen the application fields of next-generation additive manufacturing. Full article

(This article belongs to the Special Issue NextGen Materials for 3D Printing)

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Other

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7406 KiB

Open AccessFeature PaperViewpoint

Grain Structure Control of Additively Manufactured Metallic Materials

by Fuyao Yan, Wei Xiong and Eric J. Faierson

Materials 2017, 10(11), 1260; https://doi.org/10.3390/ma10111260 - 02 Nov 2017

Cited by 236 | Viewed by 17348

Abstract

Grain structure control is challenging for metal additive manufacturing (AM). Grain structure optimization requires the control of grain morphology with grain size refinement, which can improve the mechanical properties of additive manufactured components. This work summarizes methods to promote fine equiaxed grains in both the additive manufacturing process and subsequent heat treatment. Influences of temperature gradient, solidification velocity and alloy composition on grain morphology are discussed. Equiaxed solidification is greatly promoted by introducing a high density of heterogeneous nucleation sites via powder rate control in the direct energy deposition (DED) technique or powder surface treatment for powder-bed techniques. Grain growth/coarsening during post-processing heat treatment can be restricted by presence of nano-scale oxide particles formed in-situ during AM. Grain refinement of martensitic steels can also be achieved by cyclic austenitizing in post-processing heat treatment. Evidently, new alloy powder design is another sustainable method enhancing the capability of AM for high-performance components with desirable microstructures. Full article

(This article belongs to the Special Issue NextGen Materials for 3D Printing)

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