3D Printing of Polymer Nanocomposites via Stereolithography

Additive manufacturing (AM) is still underutilized as an industrial process, but is quickly gaining momentum with the development of innovative techniques and materials for various applications. In particular, stereolithography (SLA) is now shifting from rapid prototyping to rapid manufacturing, but is facing challenges in parts performance and printing speed, among others. This review discusses the application of SLA for polymer nanocomposites fabrication to show the technology's potential in increasing the applicability of current SLA‐printed parts. Photopolymerization chemistry, nanocomposite preparation, and applications in various industries are also explained to provide a comprehensive picture of the current and future capabilities of the technique and materials involved.

     

3D打印超拉伸凝胶电解质及其在柔性铝空气电池中的应用

采用细菌纤维素（BC）、聚乙烯醇（PVA）为原料，通过3D打印与冻融循环法制备超拉伸凝胶电解质。采用SEM、接触角测量、XRD、EIS和拉伸测试对凝胶电解质物理特性、电化学性能及拉伸性能进行表征。实验结果表明，当m(BC)∶m(PVA)=0.6∶1时，基于3D打印制备的凝胶电解质具有稳定的三维网络结构、优异的拉伸性能和电化学性能，拉伸强度可达0.9 MPa、断裂伸长率可达961%、离子电导率为1.10×10-1 S/cm。将该凝胶电解质应用于柔性铝空气电池，功率密度可达21 mW/cm2，电流密度为20 mA/cm2时，铝阳极比容量为1124 mA?h/g，电池可稳定放电90 min。     

Nanomaterials for 3D Printing of Polymers via Stereolithography: Concept,Technologies, and Applications

Stereolithography (SLA) is an additive manufacturing method with one of the highest accuracies (down to 100 nm) of all solid freeform techniques and has been used in various areas, such as medicine, automotive, aerospace, electronics, and others. However, most resins available nowadays are derived from petroleum. Its toxicity, low biocompatibility, and growing environmental concerns are limiting its application. This review discusses the development of biobased and biocompatible materials for different SLA processes as well as the usage of nanocomposites to increase their applicability. A comprehensive overview of the SLA technologies, photopolymerization chemistry, and resin properties are also provided. Finally, various examples using different types of materials are explored, to show the current and future capabilities of the SLA technique.     

基于3D打印技术制造柔性传感器研究进展

与传统的涂覆、沉积等加工手段相比,使用3D打印技术可制造复杂立体功能结构的传感器,将3D打印与柔性传感技术结合可以促进未来生物医疗、人工智能等领域的发展。本文介绍了国内外基于3D打印技术制造柔性传感器的最新进展,其中包括聚酰亚胺等多种基底材料、纳米金属等多种打印传感材料;按照熔融沉积、黏弹性墨水沉积、粉末烧结熔化、还原光聚合和材料喷射的制造原理分别阐述了多种传感器的材料选择、成型特点,并对制造方法进行总结分析。虽然3D打印制造柔性传感器件存在着缺乏行业标准及多种类打印材料等问题,但经过不断创新与发展,3D打印将成为柔性传感领域极佳的制造手段。     

Effect of dispersants on structural integrity of 3D printed ceramics

Ceramic 3D printing based on stereolithography is an excellent alternative to overcome drawbacks of conventional subtractive manufacturing for 3D shape control. Optimization of photocurable ceramic slurry is one of the most essential conditions to achieve favorable 3D printed structures using SL. Homogeneity of ceramic particle dispersion in photocurable resin is particularly important to optimize ceramic suspension. Dispersant plays a significant role in increasing homogeneity. Dispersant in photocurable ceramic resin has an additional effect on photocurability and integrity of 3D printed green body. We herein discuss how dispersants influence 3D printing conditions based on stereolithography using various commercially available dispersants of BYK series such as BYK103, BYK111, BYK180, BYK182, and BYK2001. Both BYK111 and BYK180 showed better performances than others because of their lower volatilities under general temperature condition during a printing process. Both solubility and decomposition temperature of dispersants largely influenced the structural quality after washing and debinding processes. This study provides worthy information to design photocurable ceramic suspension for various types of ceramic materials.     

Biomimetic Polycaprolactone-Graphene Oxide Composites for 3D Printing Bone Scaffolds

Bone shows a radial gradient architecture with the exterior densified cortical bone and the interior porous cancellous bone. However, previous studies presented uniform designs for bone scaffolds that do not mimic natural bone's gradient structure. Hence, mimicking native bone structures is still challenging in bone tissue engineering. In this study, a novel biomimetic bone scaffold with Haversian channels is designed, which approximates mimicking the native bone structure. Also, the influence of adding graphene oxide (GO) to polycaprolactone (PCL)-based scaffolds are investigated by preparing PCL/GO composite ink containing 0.25% and 0.75% GO and then 3D printing scaffolds by an extrusion-based machine. Scanning electron microscopy (SEM) is used for morphological analysis. SEM reveals good printability and interconnected pore structure. The contact angle test shows that wettability reinforces with the increase of GO content. The mechanical behavior of the scaffolds under compression is examined numerically and experimentally. The results indicate that incorporation of GO can affect bone scaffolds' Young's modulus and von Mises stress distribution. Moreover, the biodegradation rates accelerate in the PCL/GO scaffolds. Biological characterizations, such as cell growth, viability, and attachment, are performed utilizing osteoblast cells. Compared to pure PCL, an enhancement is observed in cell viability in the PCL/GO scaffolds.     

3D打印凹凸棒土改性光敏树脂制备及力学性能

采用硅烷偶联剂KH550接枝改性凹凸棒土,通过超声分散和3D打印技术进一步制备了有机凹凸棒土/光敏树脂复合物。采用傅里叶变换红外光谱对改性前后的凹凸棒土结构进行了表征;通过拉伸强度和冲击强度试验对复合光敏树脂的力学性能进行了研究;采用扫描电镜观察了复合树脂冲击断面的形貌和改性凹凸棒土在树脂中的分散情况。结果表明:改性凹凸棒土的加入有助于光敏树脂韧性的提高,当添加质量分数3%时,复合光敏树脂的冲击强度最佳。     

3D-printing bionic-patterned zirconia via stereolithography promotes soft tissue integration for ceramic implants

Due to the desirable aesthetic performance, zirconia abutments attract tremendous attention in implant related restoration of the anterior zone. However, the inadequate soft tissue integration originated from the inertia surface of zirconia severely limits its application. Fabricating bionic-patterned zirconia abutments is believed to be a promising strategy to solve this puzzle. The main obstacle to fabricating bionic-pattern lies in that conventional zirconia manufacturing technology cannot precisely engineer complex micro-pattern. Notably, modern 3D printing presents a feasible way to obtain various sophisticated topological architecture. In the present study, series of bionic-patterned zirconia were fabricated by 3D printing, simulating lotus leaf, butterfly wings, shark skin, and gecko foot. The features of micro-patterns and quality of 3D printing were systematically characterized. In addition, the effect of various bionic-patterned zirconia on the behaviors of gingival fibroblasts was investigated. Results showed that zirconia with various micro-scale bionic patterns was successfully and precisely fabricated by 3D printing. Among the four types of bionic patterns, the ones that resembled the geckos’ feet or lotus leaves were the most recommended topography for cell growth and spreading, while the pattern mimicked shark skin upgraded the expression of fibroblast functional genes including Col-I, Fn, and Itgb-1 most obviously. The bionic-patterned zirconia can efficiently promote adhesion, proliferation, and related gene expression of gingival fibroblasts, indicating that bionic-patterned zirconia has great potential to promote soft tissue integration.     

3D打印制备三维石墨烯及其在水处理中的应用

石墨烯作为一类新型纳米材料,具有对水中各类污染物良好的吸附去除性能,但石墨烯纳米粉末态的性状使其在使用后难以从溶液中分离出来而造成二次污染。因此构建大体积的三维石墨烯结构,可以有效弥补水处理中纳米材料难以分离的问题。本文介绍了如今常用的三维结构制备方法,如模板法、自组装法等,但这些方法通常步骤烦琐、影响因素及所需条件较多等,在过程中易产生结构缺陷,从而影响制得的三维结构的力学性能。文中指出,3D打印法通过计算机数据调控,具有操作简便、结构设计精准、批量制备的优点,可制备出优良的三维结构体,并可通过对浆料组分的灵活调控进行改性或增加其力学性能。综上所述,配置满足3D打印黏度要求的浆料,并使制得的三维结构具备一定要求的力学性能,充分利用其精密的规模化生产,是使3D打印三维石墨烯适用于水处理的关键所在。     

Study of alumina ceramic parts fabricated via DLP stereolithography using powders with different sizes and morphologies

Selecting suitable ceramic powders for the preparation of UV-curable ceramic suspensions, which are well suited for printing processes and production of high-performance ceramic components, is a crucial factor in the practical industrial application of digital light processing (DLP) stereolithography. Therefore, this study aims to provide a comprehensive evaluation of alumina ceramic parts fabricated via DLP stereolithography using a variety of alumina powders with varying sizes and morphologies. Experiments were conducted to examine the rheological response, recoating performance, and curing behavior of UV-curable alumina suspensions. Additionally, the thermal decomposition behavior of three-dimensional (3D)-printed green-bodies, as well as the physical and mechanical properties of 3D-printed sintered alumina components were thoroughly investigated. The best physical and mechanical performances were achieved by printing 55 vol% suspensions prepared using near-spherical AA04 alumina powders (median diameter .4 μm). This study elucidates the effects of ceramic particle size and morphology on the entire technological process of DLP-based ceramic stereolithography, thereby establishing the guidelines for the fabrication of high-performance 3D-printed ceramic objects in industrial and engineering production by selecting appropriate ceramic powders.     

3D打印高分子材料研究进展

主要介绍了聚乳酸(PLA),聚己内酯(PCL),聚醚醚酮(PEEK),聚碳酸酯(PC)和丙烯腈-丁二烯-苯乙烯塑料(ABS)等在3D打印技术中的应用,并且综述了这些材料相应的改性方法以及改性材料的应用性能。通过对已有3D打印材料的改性和扩充,3D打印产品将可以广泛应用到医疗、生物组织工程、工业、军事、航空航天等领域,3D打印技术也将成为一种主流的塑料加工技术。     

Optimized preceramic polymer for 3D structured ceramics via fused deposition modeling

3D structured ceramics stemmed from preceramic polymers via additive manufacturing have attracted much attention recently. However, these polymers with high ceramic yield are so brittle that extrusion-based additive manufacturing techniques are hardly able to be utilized for assembling 3D structures. Herein, we developed a strategy to prepare feedstocks for these manufacturing techniques, i.e., utilizing a small amount of thermal-plastic polymer to optimize the preceramic polymer while good compatibility is required between the two polymers to ensure a homogeneous mixture. Polycarbosilane and polypropylene were selected as the representative materials. Polypropylene occupied a small proportion (≤5wt.%) and significantly improved the formability of the precursor. Three-dimensional SiC were obtained via fused deposition modeling combined with crosslinking and pyrolysis. The SiC ceramic filaments showed a mean tensile strength of 471 MPa. The strategy is also applicable to a large field of ceramic systems with corresponding precursor, such as sialon ceramic and multicomponent Si-based ceramics.     

On the Use of Surfactant-Complexed Chitosan for Toughening 3D Printed Polymethacrylate Composites

This work reports a simple approach to prepare toughened 3D-printed polymethacrylate (PMA) composites using surfactant-modified chitosan (SMCS) particles at loadings between 2–10 wt%. Chitosan (CS) is modified with anionic surfactant, sodium dodecyl sulfate, via ionic complexation to facilitate compatibility and dispersion of CS to PMA matrix by non-covalent interactions between the components. The study successfully demonstrates high-accuracy 3D printing of composites with significant improvements in the overall mechanical properties. The composite with the best loading of 8 wt% SMCS shows a tensile modulus of 1.23 ± 0.05 GPa, a tensile strength at 49.8 ± 0.96 MPa, a yield stress at 33.3 ± 1.48 MPa, and a strain-at-failure 10.3 ± 0.61%, which are 45%, 40%, 32%, and 68% higher than neat PMA, respectively. This provides a significant improvement in toughness at 4.92 ± 0.55 MJ m⁻³ for the composite, 184% higher than that of neat PMA. The marked increase in toughness is due to enhanced filler-matrix interactions which improve the ability of the 3D printed composite to absorb energy under tensile load. The results from this work provide new understandings into the strategies for design and preparation of stereolithography 3D printed materials reinforced with toughening fillers from renewable resources.     

高聚物的新型3D打印材料开发进展

综述了一般3D打印技术的概念、产业及其发展。重点介绍了高聚物在3D打印材料中的应用。持续跟踪结果表明:一批新型高聚物的3D打印材料推向市场,一批国际知名化工公司也在积极介入3D打印业务。     

Synthesis of novel nanocomposites reinforced with 3D graphene/highly-dispersible nanodiamonds nano-hybrids

The phenolic resin-based ternary nanocomposites were prepared successfully by filling a three-dimensional (3D) graphene network structure embedded with highly-dispersible nanodiamonds into the resin matrix. Firstly, 3D graphene/nanodiamonds hydrogels were fabricated via self-assembly approach in a self-made dispersing medium, in which the volume ratio of ethanol absolute to deionized water was equal to 1:1. Then water molecules within the as-prepared hydrogels were replaced with resol by means of soaking and appropriate heat treatment. In-situ polymerization technique was employed subsequently to afford the ternary nanocomposites of phenolic resin/3D graphene/nanodiamonds, while the dispersion of nanodiamonds remained decent. The obtained nanocomposites exhibited high hardness and compressive strength, where the measured values were 31.1% and 24.7% higher than that of the composites procured from direct dispersion of nanodiamonds in phenolic resin matrix, respectively.     

Thiol-yne 3D Printable Polymeric Resins for the Efficient Removal of a Model Pollutant from Waters

A new 3D printable resin formulation is developed and optimized from commercially available thiol (pentaerythritol tetrakis(3-mercaptopropionate); PETMP) and alkyne (3-butyn-1-ol; BA) monomers. Printed objects are characterized by Fourier-transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). The extraction efficiency of the printed thiol-yne device is then investigated using a model dye – malachite green (MG). The results displayed excellent dye removal efficiency with > 95% MG removed within 5 min. The 3D-printed devices are reusable and show 100% removal over six cycles after washing with deionized water and methanol. The presence of surface hydroxyl groups derived from the BA monomer is shown to enhance dye adsorption in comparison to control materials. The printing procedure and resin formulation are robust and consistent when devices from different resin batches are compared for MG dye removal. The thiol-yne 3D printed devices demonstrated excellent dye removal (> 99%) from water samples collected from a tap and a nearby river source. The successful development of this resin provides a new thiol-yne-based resin system for stereolithography (SLA) 3D printing for the removal of organic dyes from wastewater and presents a potential for broad applications in water treatment.     

3D打印用高分子材料的研究进展

综述了通用塑料、工程塑料、生物塑料和光敏树脂等3D打印用材料的研究进展,分析了3D打印高分子材料面临的发展问题,提出了相应的对策。     

立体光固化3D打印成型碳化硅陶瓷的烧结特性

立体光固化(SLA)作为碳化硅陶瓷材料3D打印的主流方法之一,具有广泛的应用前景。本文针对立体光固化成型的碳化硅素坯,进行了脱脂与反应熔渗试验,通过烧结过程中密度、强度、收缩率、微观结构的变化,研究了立体光固化成型碳化硅素坯的烧结特性。结果表明:脱脂后样品具有较低的烧结收缩率,特别是增材方向,为0.88%,脱脂后的坯体强度为0.26 MPa;光敏(UV)树脂的残留热解碳(PyC)呈网状结构连接碳化硅颗粒,热解碳局部出现断裂,同时样品沿打印层间出现微裂纹;反应熔渗后残留热解碳与硅反应生成β-SiC,连续相硅填充孔隙与层间微裂纹,样品体积密度为2.79 g/cm³,抗弯强度为183.99 MPa。     

On reducing anisotropy in 3D printed polymers via ionizing radiation

The mechanical properties of materials printed using fused filament fabrication (FFF) 3D printers typically rely only on adhesion among melt processed thermoplastic polymer strands. This dramatically limits the utility of FFF systems today for a host of manufacturing and consumer products and severely limits the toughness in 3D printed shape memory polymers. To improve the interlayer adhesion in 3D printed parts, we introduce crosslinks among the polymer chains by exposing 3D printed copolymer blends to ionizing radiation to strengthen the parts and reduce anisotropy. A series polymers blended with specific radiation sensitizers, such as trimethylolpropane triacrylate (TMPTA) and triallyisocyanurate (TAIC), were prepared and irradiated by gamma rays. Differential scanning calorimetry (DSC), tensile testing, dynamic mechanical analysis (DMA) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) were employed to characterize the thermomechanical properties and the chemical structure of the various polymers. TAIC was shown to be a very effective radiation sensitizer for 3D printed sensitized polylactic acid (PLA). The results further revealed that crosslinks induced by radiation temperatures near T_g of shape memory systems have prominently enhanced the thermomechanical properties of the 3D printed polymers, as well as the solvent resistance. This enables us to deliver a new generation of inexpensive 3D printable, crosslinked parts with robust thermomechanical properties.     

Flexible and Conductive 3D Printable Polyvinylidene Fluoride and Poly(N,N‐dimethylacrylamide) Based Gel Polymer Electrolytes

In this work, 3D printable gel polymer electrolytes (GPEs) based on N,N‐dimethylacrylamide (DMAAm) and polyvinylidene fluoride (PVDF) in lithium chloride containing ethylene glycol solution are synthesized and their physicochemical properties are investigated. 3D printing is carried out with a customized stereolithography type 3D gel printer named “Soft and Wet Intelligent Matter‐Easy Realizer” and free forming GPE samples having variable shapes and sizes are obtained. Printed PVDF/PDMAAm‐based GPEs exhibit tunable mechanical properties and favorable thermal stability. Electrochemical proprieties of the printed GPEs are carried out via impedance spectroscopy in the temperature range of 25–90 °C by varying PVDF content. Ionic conductivity as high as 6.5 × 10^?4 S cm^?1 is achieved at room temperature for GPE containing low PVDF content (5 wt%) and conductivity of the GPEs is increased as temperature rises.