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As one of the most important categories in the additive manufacturing (AM) field, powder-based techniques, such as selective laser sintering, electron beam melting and selective laser ...melting, utilize laser or electronic beams to selectively fuse polymeric, metallic, ceramic or composite powders layer-by-layer into desired products according to their computer-aided design models. With unique mechanical, thermal, electrical, biocompatible and fire-retardant properties, polymeric composite materials for powder-based AM have been attracting intensive research interests because of their potential for a wide variety of functional applications in aerospace, automobile, marine and offshore, medical and many other industries.
This article provides a comprehensive review of the recent progress on polymeric composite materials, their powder preparation for AM, and functionalities and applications of their printed products. It begins with the introduction of thermoplastic polymers that have been used as the main matrices of the polymeric composites and various composite reinforcements such as metallic, ceramic, carbon-based fillers and polymer blends for strengthening and functionality purposes. Discussion is then made on the processes for manufacturing such polymeric composites into powder form, which include shear pulverization, solution-based methods and melt compounding methods, with a focus on their advantages, limitations and challenges in terms of their productivity and processibility as well as powder printability. Thereafter, the properties and functionalities of the printed products and their various intriguing applications particularly in biomedical (anatomical models, tissue engineering and drug delivery), aerospace, automobile, military, energy and environmental, acoustic devices and sports equipment are highlighted. Finally, this review is concluded with an outlook on polymeric composites for powder-based AM, new opportunities, major challenges and possible solutions.
Boosted by the success of high‐entropy alloys (HEAs) manufactured by conventional processes in various applications, the development of HEAs for 3D printing has been advancing rapidly in recent ...years. 3D printing of HEAs gives rise to a great potential for manufacturing geometrically complex HEA products with desirable performances, thereby inspiring their increased appearance in industrial applications. Herein, a comprehensive review of the recent achievements of 3D printing of HEAs is provided, in the aspects of their powder development, printing processes, microstructures, properties, and potential applications. It begins with the introduction of the fundamentals of 3D printing and HEAs, as well as the unique properties of 3D‐printed HEA products. The processes for the development of HEA powders, including atomization and mechanical alloying, and the powder properties, are then presented. Thereafter, typical processes for printing HEA products from powders, namely, directed energy deposition, selective laser melting, and electron beam melting, are discussed with regard to the phases, crystal features, mechanical properties, functionalities, and potential applications of these products (particularly in the aerospace, energy, molding, and tooling industries). Finally, perspectives are outlined to provide guidance for future research.
3D printing of high‐entropy alloys (HEAs) has great potential for manufacturing geometrically complex and/or customized HEA products with desirable performances, inspiring their increased appearance in industrial applications. A comprehensive review of the recent advances on the 3D printing of HEAs is provided, with regard to the aspects of their powder development, printing processes, microstructures, mechanical properties, functionalities, and potential applications.
Laser-based powder-bed fusion additive manufacturing or three-dimensional printing technology has gained tremendous attention due to its controllable, digital, and automated manufacturing process, ...which can afford a refined microstructure and superior strength. However, it is a major challenge to additively manufacture metal parts with satisfactory ductility and toughness. Here we report a novel selective laser melting process to simultaneously enhance the strength and ductility of stainless steel 316L by in-process engineering its microstructure into a crystallographic texture. We find that the tensile strength and ductility of SLM-built stainless steel 316L samples could be enhanced by ~16% and ~40% respectively, with the engineered textured microstructure compared to the common textured microstructure. This is because the favorable nano-twinning mechanism was significantly more activated in the textured stainless steel 316L samples during plastic deformation. In addition, kinetic simulations were performed to unveil the relationship between the melt pool geometry and crystallographic texture. The new additive manufacturing strategy of engineering the crystallographic texture can be applied to other metals and alloys with twinning-induced plasticity. This work paves the way to additively manufacture metal parts with high strength and high ductility.
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Bioprinting offers a highly-automated and advanced manufacturing platform that facilitates the deposition of bio-inks (living cells, biomaterials and growth factors) in a scalable and ...reproducible manner, a process that is lacking in conventional tissue engineering approaches. Significant improvements in the field of bioprinting have occurred over the last two decades. This reviews provides an in-depth analysis of recent improvements in the bioprinting techniques, progress in bio-ink development, implementation of new bioprinting and tissue maturation strategies. Special attention is givent to the role of polymer science and how it complements 3D bioprinting to overcome some of the major impediments in the field of organ printing. A concise overview of the anatomy and physiology of different tissues/organs is provided, followed by important design considerations to better facilitate the fabrication of biomimetic tissues/organs for tissue engineering and regenerative medicine (TERM). Last, a realistic overview of current status in organ bioprinting is presented, including recent accomplishments in bioprinting tissue-engineered constructs, the limitations and challenges, as well as opportunities for future research. We strongly believe that with the advances in polymer sciences, it will be an impending reality for on-demand bioprinting of patient-specific tissues/organs.
Re-melting strategies with same and opposite directions to the first scanning routine were performed in AlSi10Mg parts by selective laser melting (SLM) technology. Surface roughness and porosity were ...investigated with confocal microscopy, micro-computed tomography (CT) and optical microscopy (OM). Re-melting facilitates the top surface finish with Ra value decreasing from 20.67 μm to 11.67 μm (same direction) and 10.87 μm (opposite direction), almost at the same level. On side surface there is a contradictory trend. Pores at SLM parts include spherical pores due to entrapped gases, irregular pores for lack of fusion, and keyhole pores because of laser movement. The former two kinds form in the central areas while the latter one is located at edges of melting tracks and exhibits different distribution at both sides. Re-melting allows more chances for pores (spherical and keyhole pores) to escape from the melting pools. Irregular pores decrease because smoother surface allows powders to be fully melted. Porosity decrease of both re-melting strategies in central areas of the SLM parts is almost on the same level while same directional re-melting exhibits superior ability to release porosity at edges because of the porosity distribution difference at the head and wake of the melting tracks.
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•Ra value decreases on top surface but increases on side surface after re-melting.•Same directional re-melting releases more keyhole pores at edges.•Pores release is similar for same and opposite re-melting directions.
Bioprinting is a breakthrough technology that integrates living cells, biomaterials, and a robotic dispensing system to create complex structures that mimic original tissues and organs. One of the ...main components of bioprinting is bioink and hydrogel is essential in bioink formulation. In bioprinting, hydrogel should have good biocompatibility, provide good resolution, and have sufficient mechanical strength to support printed structures. Recently, thermoresponsive hydrogels have gained more and more attention due to their unique characteristic of tunable sol‐gel (liquid to solid phase) transition when temperature is changed, and many biomedical applications from drug delivery devices to tissue scaffolds have demonstrated the potentials of bioprinted thermosresponsive constructs. In this review, we discuss bioprintable thermoresponsive hydrogels with a particular focus on their gelation mechanisms, fabrication strategies using bioprinter and applications. The future prospects of the bioprinting‐based use of thermoresponsive hydrogels for next generation tissue engineering have also been discussed.
Thermoresponsive hydrogels have recently gained more and more attention to bioprinting community due to their unique characteristic of tunable sol‐gel (liquid to solid phase) transition when temperature is changed. In this review, properties, bioprinting techniques, applications, and future aspects of bioprintable thermoresponsive hydrogels are critically discussed.
Three‐dimensional (3D) printing, a layer‐by‐layer deposition technology, has a revolutionary role in a broad range of applications. As an emerging advanced fabrication technology, it has drawn ...growing interest in the field of electrochemical energy storage because of its inherent advantages including the freeform construction and controllable 3D structural prototyping. This article focuses on the topic of 3D‐printed electrochemical energy storage devices (EESDs), which bridge advanced electrochemical energy storage and future additive manufacturing. Basic 3D printing systems and material considerations are described to provide a fundamental understanding of printing technologies for the fabrication of EESDs. The performance metrics of 3D‐printed EESDs are then given and the related performance optimization strategies are discussed. Next, the recent advances of 3D‐printed EESDs, including sandwich‐type and in‐plane architectures, are summarized. Conclusions and future perspectives with some unique challenges and important directions are then discussed. It can be expected that, with the help of 3D printing technology, the development of advanced electrochemical energy storage systems will be greatly promoted.
3D‐printed electrochemical energy storage devices are an emerging research field that bridges the advanced electrochemical energy storage and future additive manufacturing. The principle material considerations, specific optimization strategies, and important advances of 3D‐printed batteries and electrochemical capacitors are highlighted. Future perspectives with some unique challenges and significant directions are also discussed.
Additive manufacturing such as selective laser sintering (SLS) offers the strategies to create 3D complex components with desirable mechanical, electrical and thermal properties using the composite ...powders as feeding materials. This work proposes a new fabrication approach to preparing carbon nanotube (CNT) composite powders and utilizes them for SLS process. As compared with the hot-compression process, the SLS process could offer an effective method to fabricate the CNT/Polymer composite with electrically conductive segregated structures. At a small loading range of CNTs (<1 wt%), the laser-sintered composites exhibit significant improvements in the electrical conductivity up to anti-static and conductive range qualifying the applications in automobile and aerospace. However, the enhancement in thermal conductivity of laser-sintered composites is not comparable with that of hot-compressed ones. The process-structure-property relationships are further investigated to study the different processes induced microstructures and the underlying mechanism of thermal and electrical performances.
The three‐dimensional (3D) printed electronics additive manufacturing industry sector has grown substantially in the past few years, and there is increasing demand for different types of metallic ...nanoparticle inks in electronics printing for various applications. Metallic nanoparticle inks are commonly used for fabricating conductive tracks and patterns due to their relatively high electrical conductivity as compared to other types of inks, and they can be further categorized into single‐element metallic nanoparticle inks, alloy metallic nanoparticle inks, metallic oxide nanoparticle inks, and core–shell bimetallic nanoparticle (BNP) inks. It is critical to gain a deep understanding of the metallic nanoparticle inks used in 3D printed electronics as the material properties of these inks can directly affect the final electrical and mechanical properties of the printed patterns. This review presents an overview of the available metallic nanoparticle inks used for 3D printing of electronics, and critically reviews the strengths and weaknesses of each type of ink. Finally, the challenges of metallic nanoparticle inks in 3D printed electronics are also discussed along with the future outlook for 3D printed electronics.
Existing research efforts that utilize different types of metallic nanoparticle inks for 3D printing of electronics in various applications are summarized. Particular attention is given to helping researchers who are exploring the use of metallic nanoparticle inks for research in 3D printing of electronics to make an informed selection of inks in their research.
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•AM processes are classified based on ISO/ASTM standard and typical commercial materials are listed.•Fundamentals of AM process categories in terms of speed, resolution and specific ...energy are discussed.•Recent applications of new additive manufacturing (AM) materials such as smart materials, ceramics, electronics, biomaterials and composites are reviewed.•3D printing is no longer a standalone process but an integral part of a multi-process system or an integrated process of multiple systems.
3D printing is emerging as an enabling technology for a wide range of new applications. From fundamentals point of view, the available materials, fabrication speed, and resolution of 3D printing processes must be considered for each specific application. This review provides a basic understanding of fundamentals of 3D printing processes and the recent development of novel 3D printing materials such as smart materials, ceramic materials, electronic materials, biomaterials and composites. It should be noted that the versatility of 3D printing materials comes from the variety of 3D printing systems, and all the new printers or processes for novel materials have not gone beyond the seven categories defined in ISO/ASTM standard. However, 3D printing should never be seen as a standalone process, it is becoming an integral part of a multi-process system or an integrated process of multiple systems to match the development of novel materials and new requirements of products.
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