Printability of elastomer latex for additive manufacturing or 3D printing

Additive manufacturing, sometimes referred to as 3D printing is a new, rapidly developing technology which has the potential to revolutionize fabrication of certain high value, complex products. Until now conventional elastomers have not been widely used in the additive manufacturing process. The goal of our work was to determine the feasibility of additive manufacturing using ink jet printing of elastomeric latex materials. Particle size, viscosity, and surface tension were measured for five different latex materials—poly(2‐chloro‐1,3‐butadiene), carboxylated styrene‐butadiene rubber, carboxylated butadiene‐acrylonitrile copolymer, natural rubber, and prevulcanized natural rubber. The XSBR latex was predicted as the one most likely to be printable. Printing trials carried out with the XSBR as the ink proved it to be printable, although technical problems of agglomeration and print head clogging need to be addressed and both the material and process need to be optimized for consistent printing to be achieved. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42931.     

Fabrication of 3D Microfluidic Channels and In‐Channel Features Using 3D Printed,Water‐Soluble Sacrificial Mold

Recent advent of additive manufacturing potentiates the fabrication of microchannels, albeit with limitations in resolution of printed structures, freedom of geometry, and choice of printable materials. Herein, a method is developed by sacrificial molding to fabricate microchannels in various polymer matrices and geometries. This method allows for rapid fabrication of 3D microchannels and channels harboring intricate in‐channel features. The method uses commercially available fused deposition modeling 3D printer and filament made of polyvinyl alcohol (PVA). Mechanically stable molds are fabricated for 3D microchannels that can be completely removed in water. Importantly, the PVA mold is stable and resilient in hydrogels despite being hygroscopic. Perfusion channels are fabricated in biocompatible substrates such as gelatin and poly(ethylene glycol) diacrylate. Fabrication of the network of 3D multilayer microchannels is demonstrated by preassembling sacrificial molds from modular pieces of molds. Intricate staggered‐herringbones grooves (SHGs) are also fabricated within microchannels to produce micromixers. The versatility and resilience of the method developed here is advantageous for biological and chemical applications that require 3D configurations of microchannels in various matrices, which would not be compatible with fabrication by direct 3D printing and softlithography.     

3D Printing Soft Matters and Applications: A Review

The evolution of nature created delicate structures and organisms. With the advancement of technology, especially the rise of additive manufacturing, bionics has gradually become a popular research field. Recently, researchers have concentrated on soft robotics, which can mimic the complex movements of animals by allowing continuous and often responsive local deformations. These properties give soft robots advantages in terms of integration and control with human tissue. The rise of additive manufacturing technologies and soft matters makes the fabrication of soft robots with complex functions such as bending, twisting, intricate 3D motion, grasping, and stretching possible. In this paper, the advantages and disadvantages of the additive manufacturing process, including fused deposition modeling, direct ink writing, inkjet printing, stereolithography, and selective laser sintering, are discussed. The applications of 3D printed soft matter in bionics, soft robotics, flexible electronics, and biomedical engineering are reviewed.     

Tough thiourethane thermoplastics for fused filament fabrication

Fused filament fabrication (FFF) is the most common form of additive manufacturing. Most FFF materials are variants of commercially available engineering plastics. Their performance when printed can widely vary, thus there is an increasing volume of research on alternative materials with thermal and mechanical performance optimized for FFF. In this work, thiol–isocyanate polymerization is used for the development of a one‐pot synthesis for polythiourethane thermoplastics for tough three‐dimensional (3D) printing applications. The thiol–isocyanate reaction mechanism allows for rapid polymer synthesis with minimal byproduct formation and few limitations on reaction conditions. The resulting elastomer has high toughness and a low melting point, making it favorable for use as a 3D printing filament. The elastomer outperforms commercial filaments in tension when printed. Considering the rapid advancement of additive manufacturing and the limitations of many engineering polymers with the 3D printing process, these results are encouraging for the development of bespoke 3D printing thermoplastics. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45574.     

基于浆料形态的陶瓷3D打印技术的浆料体系研究进展

3D打印技术因其操作简单便捷、成型快速灵活、可制备复杂结构的器件等优点,在精密陶瓷零件制造方面具有广泛应用。本文根据3D打印陶瓷的材料形态综述不同3D打印技术在陶瓷制备方面的特点,重点介绍了陶瓷3D打印成型技术中直写式3D打印、光固化3D打印、喷墨3D打印等技术所涉及的粘结剂、分散剂等组分的应用及作用机理,并对水基和非水基两种类型的添加剂组分进行总结和探讨,以期为3D打印技术制备高性能陶瓷样件提供参考。     

3D printing dielectric elastomers for advanced functional structures: A mini-review

Three-dimensional (3D) printed bionic products play an important role in intelligent robotics, microelectronics, and polymers. The printing and manufacturing process of 3D printers is conducive to obtaining soft structures that meet specific requirements, and saves time and cost. Soft intelligent robotics, an emerging research field, has always been developed based on soft materials and actuators with their biological properties. This article reviews the current understanding of 3D bioprinting technologies for dielectric elastomers (DEs), DE actuators (DEAs) and soft robots, such as inkjet, extrusion, laser-induced and stereolithography bioprinting. 3D printers for fabricating soft materials are presented and classified. The approaches to exploit 3D bioprinters for DEs/DEAs are as follows: (1) 3D printing DEAs utilize ionic hydrogel–elastomer hybrids that are analogous to human muscles, and the DEAs usually have flexible structures and large deformations with multiple functionalities. (2) An electrohydrodynamic (EHD) 3D printer confers high printing resolution and high production efficiency, which offers advantages such as full automation and flexible design. The optimal printing conditions are mainly determined by the effects of printing voltages and ink properties, which are related to the formation of the liquid cone and the printed line width. Furthermore, the advantages of 3D bioprinting technologies have accelerated their development and applications.     

Experimental investigation and optimization of printing parameters of 3D printed polyphenylene sulfide through response surface methodology

Today fused filament fabrication is one of the most widely used additive manufacturing techniques to manufacture high performance materials. This method entails a complexity associated with the selection of their appropriate manufacturing parameters. Due to the potential to replace poly-ether-ether-ketone in many engineering components, polyphenylene sulfide (PPS) was selected in this study as a base material for 3D printing. Using central composite design and response surface methodology (RSM), nozzle temperature (T), printing speed (S), and layer thickness (L) were systematically studied to optimize the output responses namely Young's modulus, tensile strength, and degree of crystallinity. The results showed that the layer thickness was the most influential printing parameter on Young's modulus and degree of crystallinity. According to RSM, the optimum factor levels were achieved at 338°C nozzle temperature, 30 mm/s printing speed, and 0.17 mm layer thickness. The optimized post printed PPS parts were then annealed at various temperatures to erase thermal residual stress generated during the printing process and to improve the degree of crystallinity of printed PPS's parts. Results showed that annealing parts at 200°C for 1 hr improved significantly the thermal, structural, and tensile properties of printed PPS's parts.     

Mechanical and dimensional performance of poly(lactic acid) 3D-printed parts using thin plate spline interpolation

In additive manufacturing, determining the correct deposition parameters is very important as this can affect the final properties of printed parts. Since there is no agreement on the optimal level of the different printing parameters in reported results, this work evaluated the influences of layer thickness (LT), deposition speed (DS) and printing direction (PD) on tensile properties and dimensional accuracy of poly(lactic acid) 3D parts evaluating the possibility of using thin plate spline interpolation method (TPSIM) of data, a new approach, in determination of optimized fused deposition modeling process parameters. It was observed that the use of low levels of LT (0.10 mm), DS (40 mm/s), and PD (0°) provided parts with higher mechanical strength and dimensional performance. Denser parts showed lower anisotropy effect and, consequently, best tensile properties were obtained. TPSIM was an efficient mathematical analysis and well fitted results of predicted and experimental results.     

陶瓷增材制造(3D打印)技术研究进展

高性能陶瓷是现代技术发展和应用不可或缺的关键材料。常规的陶瓷制造技术难以满足对个性化、精细化、轻量化和复杂化的高端产品快速制造的需求。新兴的增材制造技术(3D打印)在高性能陶瓷的成型制造领域具有巨大的发展潜力,有望突破传统陶瓷加工和生产的技术瓶颈,为陶瓷关键零部件的应用开辟新的途径。本文针对陶瓷材料及其快速成型和后处理工艺,重点阐述了三维打印技术、光固化成型技术、选择性激光烧结技术等主流陶瓷增材制造技术的研究现状,并指出了目前存在的问题及发展趋势。     

Impact Optimization of 3D‐Printed Poly(methyl methacrylate) for Cranial Implants

Material extrusion‐based additive manufacturing, also known as fused filament fabrication (FFF) or 3D printing facilitates the fabrication of cranial implants with different materials and complex internal structures. The impact behavior plays a key role in the designing process of cranial implants. Therefore, the performance of impact tests on novel implant materials is of utmost importance. This research focuses on investigating the dependency of the infill density and pattern on the impact properties of 3D‐printed poly(methyl methacrylate) (PMMA) sandwich specimens including internal rectilinear, gyroid, and 3D‐honeycomb (3D‐HC) structures. 3D‐HC structures show higher impact forces and dissipated energies as well as dynamic stiffness values compared to rectilinear and gyroid structures at the same infill density. 70% infill 3D‐HC and 100% infill rectilinear structures prove to be most promising. In addition, two different optimization techniques to further improve the impact properties of these specimens, namely a material and a topology optimization, are applied. Topology optimization shows promising results until first damage and material optimization regarding dissipated energies. However, both are not able to outperform the 3D‐HC pattern.     

3D打印成型工艺及其应用研究

从增材制造的实现原理出发,分析了当前几种主流三维（3D）成型工艺的技术特点、设备原理及实现流程。以工业级3D打印机为研究平台,将熔融沉积成型（FDM）工艺应用于复杂型腔结构和传动组件结构的快速成型,通过3D建模、数据转化、切片处理、工艺参数选择、模型包计算及工艺后处理等一系列环节的实践探索,明确了FDM成型工艺的技术原理与应用流程,并成功制作了丙烯腈丁二烯苯乙烯共聚物（ABS）材质的3D打印模型。结果表明,复杂型腔零件切片厚度为0.254 mm、传动组件切片厚度为0.178 mm时,3D成型件具有理想的工艺精度和打印效率。     

A review of 3D printed porous ceramics

Three-dimensional (3D) printing of ceramics has gained widespread attentions in recent years. Many excellent reviews have reported the printing of ceramics. However, most of them focus on printing of dense ceramics or general ceramic aspects, there is no systematical review about 3D printing of porous ceramics. In this review paper, the 3D printing technologies for fabricating of porous ceramic parts are introduced, including binder jetting, selective laser sintering, direct ink writing, stereolithography, laminated object manufacturing, and indirect 3D printing processes. The techniques to fabricate hierarchical porous ceramics by integrating 3D printing with one or more conventional porous ceramics fabrication approaches are reviewed. The main properties of porous ceramics such as pore size, porosity, and compressive strength are discussed. The emerging applications of 3D printed porous ceramics are presented with a focus on the booming application in bone tissue engineering. Finally, summary and a perspective on the future research directions for 3D printed porous ceramics are provided.     

Optimization of printing parameters for improvement of mechanical and thermal performances of 3D printed poly(ether ether ketone) parts

Many processing parameters can be adjusted to optimize the fused filament fabrication (FFF) process, a popular and widely used additive manufacturing techniques for plastic materials. Among those easily adjusted parameters are the nozzle temperature, printing speed, raster orientation, and layer thicknesses. Using poly(ether ether ketone) (PEEK) as the base material, a design of experiments analysis was performed on the main FFF parameters. A response surface methodology was applied to analyze the results and to maximize the output responses. Results have shown that the nozzle temperature is the most influential parameter on tensile properties and the crystallinity degree of printed PEEK by FFF process. Parts produced with optimized FFF parameters were then subjected to an annealing treatment to induce a relaxation of residual stress and to enhance crystallinity. The best properties for 3D printed PEEK parts were achieved with annealed parts prepared at 400°C with a printing speed of 30 mm/s, 0.15 mm layer thickness and raster orientation of [0°/15°/−15°]. The resulting parts have mechanical properties comparable to those of injected PEEK.     

3D Printing for Tissue Engineering

Tissue engineering aims to fabricate functional tissue for applications in regenerative medicine and drug testing. More recently, 3D printing has shown great promise in tissue fabrication with a structural control from the micro- to the macroscale by using a layer-by-layer approach. Whether through scaffold-based or scaffold-free approaches, the standard for 3D-printed tissue engineering constructs is to provide a biomimetic structural environment that facilitates tissue formation and promotes host tissue integration (e.g., cellular infiltration, vascularization, and active remodeling). This review will cover several approaches that have advanced the field of 3D printing through novel fabrication methods of tissue engineering constructs. It will also discuss the applications of synthetic and natural materials for 3D printing facilitated tissue fabrication.     

双光子聚合3D打印

3D打印是一种快速成型的增材制造技术。光固化立体印刷(SLA)是技术较成熟和应用较广的一种3D打印技术。SLA是采用紫外激光的单光子聚合过程,其加工分辨率受经典光学衍射极限的限制,难以满足分辨率高的微纳结构的加工。不同于SLA,利用近红外波长飞秒激光的双光子聚合3D打印技术可以突破经典光学衍射的限制,制造分辨率高的纳米尺度任意形状三维结构。本文将介绍双光子吸收和双光子聚合的原理、双光子聚合的发展和双光子聚合3D打印技术的应用,最后对该技术的发展进行展望。     

Plastics Engineering's New Frontier: Embracing the Brave New World of 3D Printing

The Toly Group is a small manufacturer on the island of Malta that creates packaging for the cosmetics industry: lipstick holders, compacts, cream jars and bottles, and the like. Thanks to three‐dimensional (3D) printing (also known as additive manufacturing), the company is able to rapidly prototype design variants to determine shape and use with its customers—and showcase proposed designs before a purchase and production decision is made. The flexibility and low cost of 3D printing makes a fast turnaround possible.     

Nanogrooved carbon microtubes for wet three‐dimensional printing of conductive composite structures

Recent advances in three‐dimensional (3D) printing have enabled the fabrication of interesting structures which are not achievable using traditional fabrication approaches. The 3D printing of carbon microtube composite inks allows fabrication of conductive structures for practical applications in soft robotics and tissue engineering. However, it is challenging to achieve 3D printed structures from solution‐based composite inks, which requires an additional process to solidify the ink. Here, we introduce a wet 3D printing technique which uses a coagulation bath to fabricate carbon microtube composite structures. We show that through a facile nanogrooving approach which introduces cavitation and channels on carbon microtubes, enhanced interfacial interactions with a chitosan polymer matrix are achieved. Consequently, the mechanical properties of the 3D printed composites improve when nanogrooved carbon microtubes are used, compared to untreated microtubes. We show that by carefully controlling the coagulation bath, extrusion pressure, printing distance and printed line distance, we can 3D print composite lattices which are composed of well‐defined and separated printed lines. The conductive composite 3D structures with highly customised design presented in this work provide a suitable platform for applications ranging from soft robotics to smart tissue engineering scaffolds. © 2019 Society of Chemical Industry     

3D printed carbon-ceramic structures for enhancing photocatalytic properties

3D printing creates structures from digitally designed models by bottom-up fabrication method, achieving excellent control of target structures from various materials. Compared with conventional manufacturing methods such as machining, chemical engineering and bio-template, 3D printing shows advantages in aspects of parameterization-designed structure, rapid preparation, high precision and low cost. Herein, 3D printed carbon-ceramic support with designed array patterns, square, circular and diamond, was fabricated in an inert atmosphere to obtain sophisticated pore structure with high surface area. The existence of pyrolyzed carbon from UV-curable resin suppressed the mass transfer process when sintering and was found to greatly increase pore area from 0.067 m²/g to 0.509 m²/g. Molybdenum disulfide (MoS₂) chosen as a typical catalyst was loaded on the sintered support. The photodegradation efficiency of as-printed carbon support with MoS₂ increased to 45.95% while that of pure MoS₂ was only 23.35%. The catalyst-support system showed significant stability and the efficiency decreased to 82.35% after five cycles. UV–Vis diffused reflectance spectra proved that pyrolyzed carbon increased the light adsorption efficiency at the whole range of visible light.     

Fabrication of hierarchical lattice structures from zirconia stabilized ceramics by micro-SLA 3D printing approach

The need for the new materials and advanced manufacturing techniques for achieving the highest characteristics of energy devices is an obvious trend. One of the possible ways to create structures for energy applications is to introduce complex geometries and promising features with additive manufacturing (AM). Using this approach, it is possible to create complex geometry and moreover decrease the weight of materials. In this paper, we developed the layer-by-layer fabrication approach of ceramic hierarchical lattice structures via the (micro-SLA) technology. As a feedstock material, the novel composition of partly stabilized-zirconia ceramics (6ScSZ, 8YSZ) was developed. Materials were selected as a solid slurry component due to high ionic conductivity at the working temperature of modern solid oxide fuel cells (SOFCs). For the sintering, the green body heat treatment process was optimized to one step, which decrease the time and production cost. The data from scanning electron microscopy and micro-CT shows that 112-layer samples of the octet truss did not show any critical defects, and the achieved relative density was close to the theoretical one. Totally, 22 samples with the total size of 6.5 mm * 6.5 mm * 2.8 mm and the diameter of struts in the range of 240–250 μm were fabricated at a rate of only 56 min per sample, using two modifications of advanced doped zirconia-ceramics. This study opens new opportunities for the development and transfer to the production of additive manufacturing of ceramics to build energy systems devices such as solid oxide fuel cells.