Jet 3D Printing Research Articles

Influence of initial relative densities on the sintering behavior and mechanical behavior of 316 L stainless steel fabricated by binder jet 3D printing

Compared with other 3D printing methods, binder jet 3D printing (BJ3DP) shows the great potential for obtaining large-scale complex parts with high efficiency and low cost. However, understanding the sintering behavior of powders is one of the challenging topics in BJ3DP. In this work, on the basis of the thermo–elasto–viscoplastic constitutive law model, the sintering behavior of 316 L stainless steel (316 L SS) cuboids prepared by BJ3DP with different initial relative densities (relative densities of green parts), i.e., 49.5%, 51.5% and 53.5%, was investigated via finite-element numerical simulations. It suggested that the shrinkage decreased as the initial relative density increased, resulting from that a higher initial relative density would provide higher sintering stress. Additionally, precise shrinkage and final relative densities of the BJ3DP samples were quantitatively predicted via numerical simulations, and the simulated results were in good agreement with experimental results. According to the experimental results, a final relative density of ~98.7% could be achieved in the BJ3DP 316 L SS sample with an initial relative density of 53.5% after sintering, showing a yield strength of ~308 MPa and an ultimate tensile strength of ~601 MPa along with a total elongation of ~59.4%.

A general fruit acid chelation route for eco-friendly and ambient 3D printing of metals

Recent advances in metal additive manufacturing (AM) have provided new opportunities for prompt designs of prototypes and facile personalization of products befitting the fourth industrial revolution. In this regard, its feasibility of becoming a green technology, which is not an inherent aspect of AM, is gaining more interests. A particular interest in adapting and understanding of eco-friendly ingredients can set its important groundworks. Here, we demonstrate a water-based solid-phase binding agent suitable for binder jetting 3D printing of metals. Sodium salts of common fruit acid chelators form stable metal-chelate bridges between metal particles, enabling elaborate 3D printing of metals with improved strengths. Even further reductions in the porosity between the metal particles are possible through post-treatments. A compatibility of this chelation chemistry with variety of metals is also demonstrated. The proposed mechanism for metal 3D printing can open up new avenues for consumer-level personalized 3D printing of metals.

Characterization of radiation damage in 3D printed SiC

• High-purity SiC composites fabricated by additive manufacturing were irradiated. • Radiation-induced defects are easily observed in α-SiC particles but not CVI matrix. • Defect swelling measured by STEM-EELS is similar in α-SiC particles and CVI matrix. • Defect types and swelling are consistent with other forms of nuclear-grade SiC. • Interface denuded zone reveals sink strength bias and relative defect-type mobility. The SiC fuel matrix for advanced gas-cooled high temperature reactors as part of the Transformational Challenge Reactor program serves as the fuel particle container structure, a barrier to fission gas release, and a heat transfer medium. Its performance is particularly important because the fuel matrix must demonstrate good structural stability and thermal behaviors. An additive manufacturing methodology combining a binder jet 3D printing process with chemical vapor infiltration (CVI) for the production of SiC was recently developed. In this study, post irradiation examination by transmission electron microscopy shows that defect accumulation within the printed particles is very similar to other forms of high-purity SiC. However, damage accumulation was not directly observed in the CVI matrix because black spot damage and dislocation loops are difficult to image within the nanoscale highly faulted CVI matrix and because interstitial defects may rapidly annihilate at the stacking faults. Therefore, electron energy loss spectroscopy (EELS) analysis was used to analyze defect swelling in both the printed particles and the CVI matrix. The EELS analysis helped reveal that the radiation-induced swelling in the CVI matrix is similar to that of the printed SiC particles. This work shows that 3D printed SiC has behavior that is comparable to SiC processed by other means and that 3D printing could serve as a suitable processing technique for high-purity SiC for nuclear applications.

Bending behavior of 3D printed mechanically robust tubular lattice metamaterials

Tubular lattice structures have gained tremendous attention due to their lightweight and excellent mechanical properties. In this work, we designed a new type of tubular lattice architecture by rolling up planar lattice structures with a negative Poisson’s ratio, and then fabricated samples using a material jetting 3D printing technique. We investigated their bending behavior under large deformation using a combined experimental and numerical approach. It was found that the proposed auxetic tubular lattice (ATL) structure exhibits a more compliant behavior, and the ductility increased by up to 85.4% compared to that of a conventional diamond tubular lattice (DTL) structure. Meanwhile, the ATL structure is characterized by a local bending behavior due to the auxetic effect, while the DTL structure is featured with global bending mode. Finite element simulations further reveal that the stress on the ATL structure distributes locally around the indenter. In contrast, stress on the DTL structure distributes much more uniformly across the span. As such, the ATL structures exhibit excellent global stability compared to the DTL structure. Our parametric study shows that bending stiffness, maximum load, and ductility of the proposed ATL structure are mainly controlled by beam depth, due to its large exponential contribution to the moment of inertia. Increasing beam depth leads to a more desirable ductility than increasing beam thickness. The beam amplitude and tubular curvature have minor effects on the bending performance compared to other geometric parameters. The findings reported in this work can guide designing and optimizing mechanically robust tubular lattice metamaterials for applications in tissue engineering, biomedical devices, and robotics engineering.

N protein-based ultrasensitive SARS-CoV-2 antibody detection in seconds via 3D nanoprinted, microarchitected array electrodes.

Rapid detection of antibodies to SARS‐CoV‐2 is critical for COVID‐19 diagnostics, epidemiological research, and studies related to vaccine evaluation. It is known that the nucleocapsid (N) is the most abundant protein of SARS‐CoV‐2 and can serve as an excellent biomarker due to its strong immunogenicity. This paper reports a rapid and ultrasensitive 3D biosensor for quantification of COVID‐19 antibodies in seconds via electrochemical transduction. This sensor consists of an array of three‐dimensional micro‐length‐scale electrode architecture that is fabricated by aerosol jet 3D printing, which is an additive manufacturing technique. The micropillar array is coated with N proteins via an intermediate layer of nano‐graphene and is integrated into a microfluidic channel to complete an electrochemical cell that uses antibody‐antigen interaction to detect the antibodies to the N protein. Due to the structural innovation in the electrode geometry, the sensing is achieved in seconds, and the sensor shows an excellent limit of detection of 13 fm and an optimal detection range of 100 fm to 1 nm. Furthermore, the sensor can be regenerated at least 10 times, which reduces the cost per test. This work provides a powerful platform for rapid screening of antibodies to SARS‐CoV‐2 after infection or vaccination.

Review of binder jetting 3D printing in the construction industry

Review of binder jetting 3D printing in the construction industry

Evaluation of the Mechanical and Photocatalytic Properties of Tio2-Reinforced Cement-Based Material in Binder Jet 3d Printing

Evaluation of the Mechanical and Photocatalytic Properties of Tio2-Reinforced Cement-Based Material in Binder Jet 3d Printing

Binder Jet 3d Printing of Biomedical Grade Ti-6al-4v Alloy: The Role of Particle Size, Microstructural Features, and Mechanical Properties

Binder Jet 3d Printing of Biomedical Grade Ti-6al-4v Alloy: The Role of Particle Size, Microstructural Features, and Mechanical Properties

A multi-scale E-jet 3D printing regulated by structured multi-physics field

Micro/nano scale structure as important functional part have been widely used in wearable flexible sensors, gas sensors, biological tissue engineering, microfluidic chips super capacitors and so on. Here a multi-scale electrohydrodynamic jet (E-jet) 3D printing approach regulated by structured multi-physics fields was demonstrated to generate 800 nm scale 2D geometries and high aspect ratio 3D structures. The simulation model of jetting process under resultant effect of top fluid field, middle electric field and bottom thermal field was established. And the physical mechanism and scale law of jet formation were studied. The effects of thermal field temperature, applied voltage and flow rate on the jet behaviors were studied; and the range of process parameters of stable jet was obtained. The regulation of printing parameters was used to manufacture the high resolution gradient graphics and the high aspect ratio structure with tight interlayer bonding. The structural features could be flexibly adjusted by reasonably matching the process parameters. Finally, polycaprolactone/polyvinylpyrrolidone (PCL/PVP) composite scaffolds with cell-scale fiber and ordered fiber spacing were printed. The proposed E-jet printing method provides an alternative approach for the application of biopolymer materials in tissue engineering.

In Vitro and In Vivo Bioequivalence Study of 3D-Printed Instant-Dissolving Levetiracetam Tablets and Subsequent Personalized Dosing for Chinese Children Based on Physiological Pharmacokinetic Modeling.

Recently, the development of Binder Jet 3D printing technology has promoted the research and application of personalized formulations, which are especially useful for children’s medications. Additionally, physiological pharmacokinetic (PBPK) modeling can be used to guide drug development and drug dose selection. Multiple technologies can be used in combination to increase the safety and effectiveness of drug administration. In this study, we performed in vivo pharmacokinetic experiments in dogs with preprepared 3D-printed levetiracetam instant-dissolving tablets (LEV-IDTs). Bioequivalence analysis showed that the tablets were bioequivalent to commercially available preparations (Spritam®) for dogs. Additionally, we evaluated the bioequivalence of 3D-printed LEV-IDTs with Spritam® by a population-based simulation based on the established PBPK model of levetiracetam for Chinese adults. Finally, we established a PBPK model of oral levetiracetam in Chinese children by combining the physiological parameters of children, and we simulated the PK (pharmacokinetics) curves of Chinese children aged 4 and 6 years that were administered the drug to provide precise guidance on adjusting the dose according to the effective dose range of the drug. Briefly, utilizing both Binder jet 3D printing technology and PBPK models is a promising route for personalized drug delivery with various age groups.

Enhancing drop mixing in powder bed by alternative particle arrangements with contradictory hydrophilicity

BackgroundDrop mixing in porous media is critical to printing quality of inkjet printing and binder jetting 3D printing, however, the mixing is poor due to restricted pore space. In this study, an alternative hydrophobic/hydrophilic particle arrangement was proposed to enhance dual droplets mixing in a powder bed. MethodsA computational fluid dynamic (CFD) model was first developed to simulate the fluid flow for drops falling on a powder bed by using volume of fluid (VOF) technique. Two drops containing separate solutes sequentially impact an assembly of particles. An index of mixing was proposed to quantitatively describe the degree of mixing by calculating the standard deviation of species concentrations. Significant FindingsTo enhance mixing, a new approach was developed to improve liquid mixing by arranging hydrophobic/hydrophilic particles alternatively. Furthermore, drops falling with a horizontal offset was shown to prolong the vorticity for convective mass transportation. With an optimal offset distance of 15μm, the mixing degree can be enhanced from 34.2% to 56.2%. The printing strategy developed from this study could apparently enhance drop mixing in porous media and provided potential developments for multiple-component mixing in binder jetting 3D printing.

Chloride Diffusion by Build Orientation of Cementitious Material-Based Binder Jetting 3D Printing Mortar.

Binder jetting 3D printing (BJ3DP) is used to create geometrical and topology-optimized building structures via architectural geometric design owing to its high degree of freedom in geometry implementation. However, building structures require high mechanical and durability performance. Because of the recent trend of using 3D printing concrete as a structural component in reinforcing bars, its durability with respect to chloride penetration needs to be reviewed. Therefore, in this study, the compressive strength and durability of the chloride diffusion of cement-based 3D-printed output were evaluated. In addition, to confirm the performance difference based on the build orientation, the compressive strength and chloride diffusion were evaluated with respect to the build direction and transverse direction. The experimental results show that the compressive strength was approximately 22.1–26.5% lower in the transverse direction than in the build direction and that the chloride diffusion coefficient was approximately 186.1–407.1% higher in the transverse direction. Consequently, when a structure that requires long-term durability is produced using BJ3DP, it is necessary to examine the design and manufacturing methods in relation to the build orientation in advance.

Combining powder bed compaction and nanopowders to improve density in ceramic binder jetting additive manufacturing

This paper reports a new approach to density improvement in ceramic binder jetting additive manufacturing: combining powder bed compaction and nanopowders. Samples were printed on a commercially available binder jetting 3D printer using an alumina nanopowder. Compaction thickness was varied across 0, 5, 10, 15, 20, and 60 μm at a layer thickness of 5 μm, and across 0, 100, and 200 μm at a layer thickness of 30 μm. Sintered density, as well as powder bed density, was measured. Furthermore, microstructure of sintered samples, with a focus on number and size of pores, was investigated to substantiate the density results. It was shown that at the same layer thickness, higher compaction thickness resulted in higher powder bed density, higher sintered density, and smaller number and size of pores in sintered samples. The highest sintered density (72.0%) achieved in this study was on par with the highest density reported in the literature on binder jetting of alumina without involving unusual liquid feedstocks or special post-processing techniques, demonstrating the effectiveness of this new approach to density improvement.

Binder jetting 3D printing of challenging medicines: From low dose tablets to hydrophobic molecules

Increasing access to additive manufacturing technologies utilising easily available desktop devices opened novel ways for formulation of personalized medicines. It is, however, challenging to propose a flexible and robust formulation platform which can be used for fabrication of tailored solid dosage forms composed of APIs with different properties (e.g., hydrophobicity) without extensive optimization. This manuscript presents a strategy for formulation of fast dissolving tablets using binder jetting (BJ) technology. The approach is demonstrated using two model APIs: hydrophilic quinapril hydrochloride (QHCl, logP = 1.4) and hydrophobic clotrimazole (CLO, logP = 5.4). The proposed printing method uses inexpensive, well known, and easily available FDA approved pharmaceutical excipients. The obtained model tablets had uniform content of the drug, excellent mechanical properties, and highly porous structure resulting in short disintegration time and fast dissolution rate. The tablets could be scaled and obtained in predesigned shapes and sizes. The proposed method may find its application in the early stages of drug development where high flexibility of the formulation is required and the amount of available API is limited.

Microstructure evolution for isothermal sintering of binder jet 3D printed alloy 625 above and below the solidus temperature

When compared to beam-based melting methods, binder jet 3D printing is less time consuming, and the printed material is less prone to residual stresses. However, binder jet printing often contains remnant porosity that survives pressureless sintering and limits the mechanical properties of metals including fatigue strength and ductility. In this work, gas atomized nickel-based superalloy 625 powders with three different particle size distributions are binder jet printed and subsequently isothermally sintered at subsolidus and supersolidus temperatures. Individual feature measurements were conducted on two-dimensional sections and pore size distribution frequencies were plotted to reveal the difference in microstructural evolution between subsolidus and supersolidus sintering. Supersolidus liquid phase sintering is thought to have facilitated particle rearrangement under the surface tension of the liquid phase, resulting in a homogeneous microstructure that favored subsequent densification and higher final density. Additionally, printed powder with a wide particle size distribution not only reached high green density of ~52%, but also achieved final densities above 99%.

Binder Jet 3D Printing of Compound LEV-PN Dispersible Tablets: An Innovative Approach for Fabricating Drug Systems with Multicompartmental Structures.

Three-dimensional (3D) printing is an emerging technology that has high application potential for individualized medicines and complex solid dosage forms. This study is designed to explore binder jet 3D printing (BJ-3DP) for the development of high-precision and repeatable compound levetiracetam-pyridoxine hydrochloride (LEV-PN) multicompartmental structure dispersible tablets. PN was dissolved in printing ink directly and accurately jetted into the middle, nested layer of the tablet, and precise control of the drug dose was achieved through the design of printing layers. With modification of the drying method, the “coffee ring” effect caused by drug migration during the curing and molding of the tablets was overcome. Furthermore, 3D topography showed that the tablets have a promising surface morphology. Scanning electron microscopy and porosity results indicated that the tablets have a loose interior and tight exterior, which would ensure good mechanical properties while enabling the tablet to disintegrate quickly in the mouth and achieve rapid release of the two drugs. This study used BJ-3DP technology to prepare personalized multicompartmental structures of drug systems and provides a basis for the development of complex preparations.

Three-Dimensional RAW264.7 Cell Model on Electrohydrodynamic Printed Poly(ε-Caprolactone) Scaffolds for In Vitro Study of Anti-Inflammatory Compounds

Inflammation plays an essential role in the human immune system, and anti-inflammatory compounds are important to promote health. However, the in vitro screening of these compounds is largely dependent on flat biology. Herein, we report our efforts in establishing a 3D inflammation murine macrophage model. Murine macrophage RAW 264.7 cells were cultured on poly(ε-caprolactone) (PCL) scaffolds fabricated through an electrohydrodynamic jetting 3D printer and their behavior were examined. Cells on PCL scaffolds showed a 3D shape and morphology with multilayers and a lower proliferation rate. Moreover, macrophages were not activated by scaffold material PCL and 3D microenvironment. The 3D cells showed greater sensitivity to lipopolysaccharide stimulation with higher production activity of nitric oxide (NO), nitric oxide synthases (iNOS), and cyclooxygenase-2 (COX-2). Additionally, the 3D macrophage model showed lower drug sensitivity to commercial anti-inflammatory drugs including aspirin, ibuprofen, and dexamethasone, and natural flavones apigenin and luteolin with higher IC50 for NO production and lower iNOS and COX-2 inhibition efficacy. Overall, the 3D macrophage model showed promise for higher accurate screening of anti-inflammatory compounds. We developed, for the first time, a 3D macrophage model based on a 3D-printed PCL scaffold that provides an extracellular matrix environment for cells to grow in the 3D dimension. 3D-grown RAW 264.7 cells showed different sensitivities and responses to anti-inflammatory compounds from its 2D model. The 3D cells have lower sensitivity to both commercial and natural anti-inflammatory compounds. Consequently, our 3D macrophage model could be applied to screen anti-inflammatory compounds more accurately and thus holds great potential in next-generation drug screening applications.

Machine learning for 3D printed multi-materials tissue-mimicking anatomical models

Polyjet, a material jetting 3D printing technique, has been widely used for the fabrication of patient-specific anatomical models owing to the toolless fabrication technique and its ability to print multiple materials in a single part. Although the fabrication of anatomical models with high dimensional accuracy has been demonstrated, 3D printed anatomical models with tissue-mimicking properties have not been realized. In this study, a composite layering design was used to tune the shore hardness and compressive modulus of the Polyjet-printed parts in an attempt to mimic the properties of human tissues. 216 specimens (with 72 combinations of design parameters) were printed and tested to develop the material library for the anatomical models. An analytical model was developed to estimate the effective compressive modulus and shore hardness of the composite laminate. A neural network was used to learn the multi-dimensional relationship between the design parameters and mechanical properties. The 5-33-2 network size is found to be the optimum neural network structure with a mean square error of 0.98% for the compressive modulus, lower than the traditional response surface method model. A genetic algorithm was used to search the design space for the most optimum design parameters for the targeted effective shore hardness.

The effects of sintering temperature and hold time on densification, mechanical properties and microstructural characteristics of binder jet 3D printed 17-4 PH stainless steel

In this study, the influence of sintering temperature and hold time on densification, mechanical properties, and microstructural characteristics of 17–4 PH stainless steel samples produced by binder jet 3D printing (BJ3DP) was investigated. An ultimate tensile strength (UTS) of 1050 MPa, an elongation at break (A) of >4% and a hardness of ≥330 HV10 through sintering at 1300 °C for 90 min were achieved. The tensile properties are predominantly influenced by porosity as opposed to the grain size or the volume fraction of δ-ferrite. A layered porosity appears in the sintered parts, which is attributed to the layer-wise BJ3DP process. Shrinkage in z-direction is about 2% higher than in x- and y-direction and is therefore anisotropic. Fluctuations in green density of up to 1.2% affect sintered density throughout the study and are compensated best by extended hold times. Microstructural analyses show the expected grain growth and increase in δ-ferrite fraction by increasing sintering temperature and more extensive hold times, while the comparison of fringe and core microstructures reveals little differences of the grain size but significant differences of the fraction of δ-ferrite and porosity.

Pharmaceutical applications of powder-based binder jet 3D printing process - A review.

Pharmaceutical applications of the 3D printing process have recently matured, followed by the FDA approval of Spritam, the first commercial 3D printed dosage form. Due to being a new technology in the conventional dosage formulation field, there is still a dearth of understanding in the 3D printing process regarding the effect of the raw materials on the printed dosage forms and the plausibility of using this technology in dosage development beyond the conventional ways. In this review, the powder-based binder jet 3D printing (BJ3DP) process and its pharmaceutical applications have been discussed, along with a perspective of the formulation development step. The recent applications of BJ3DP in pharmaceutical dosage development, the advantages, and limitations have further been discussed here. A discussion of the critical formulation parameters that need to be explored for the preformulation study of the solid oral dosage development using the BJ3DP process is also presented.