Three-dimensional Additive Manufacturing Research Articles

Feature-based energy consumption quantitation strategy for complex additive manufacturing parts

Additive manufacturing (AM) has significant advantages, including design freedom, mass customization, and complex-structure manufacturing capabilities. As reducing the manufacturing energy is challenging in terms of the industrial sustainability, the AM energy consumption must be further explored. Existing energy consumption quantitation methods for AM require complex models that considering the energy characteristics of equipment. Therefore, we propose a feature-based energy consumption quantitation method for complex AM parts using simple models and suitable for different AM technologies. First, a feature segmentation method is proposed to divide complex AM parts into typical AM features. Then, the energy consumption model for each AMF is developed for energy consumption quantification during part fabrication. Finally, the energy consumption of a typical mechanical part manufactured via three different AM processes is investigated using the proposed method and measured experimentally. The results show that the proposed method can effectively and rapidly predict the energy consumption of AM processes with an accuracy of more than 95 %. Furthermore, the efficiency of the three AM processes is compared and discussed to address suitable efficiency improvement methods. In general, the proposed method can be integrated into three-dimensional AM models, providing a reference for the structural optimization of AM parts and sustainable manufacturing.

Q-band balanced bandpass filter based on rectangular micro-coaxial transmission line with improved common-mode suppression

This paper presents a novel design of a wideband millimeter-wave balanced bandpass filter (BPF) for use in a high-sensitivity Q-band reception system for solar radio spectrum observation. The balanced BPF has differential-mode (DM) band-pass and common-mode (CM) band-stop characteristics, which effectively suppress noise and reduce electromagnetic interference in its operating frequency band. The filter design incorporates half-wavelength rectangular micro-coaxial transmission lines as resonators and coupling between resonators is achieved through J-inverters. The wideband CM suppression is improved by adjusting the distribution of CM transmission zeros by adding open-circuited branches on the symmetrical plane. The micro-coaxial structure is fabricated on a 4-inch silicon wafer through a three-dimensional additive manufacturing process. The compactness, low loss, and wideband performance make it ideal for this application. As a design example, a fifth-order Chebyshev balanced BPF was fabricated and measured to demonstrate the design method. The measured results indicate that the balanced BPF operates within a frequency range of 30–50 GHz, with an insertion loss of 1.63 dB and over 26 dB CM suppression in the DM passband. These results are in general agreement with simulation results. To the best of our knowledge, this is the first time that a micro-coaxial structure has been proposed for this application.

Electrospray printing: Unravelling the history of a support free three-dimensional additive manufacturing technology

In this perspective article the author highlights a revolutionary technology, which makes reality, the ability to print true three-dimensional architectures, containing self-standing and self-supporting overhangs in the nano and micrometer scale, without the need for supports of any kind. There have been many attempts to achieve this feature in the rapid prototyping/additive manufacturing fields but has been met with little or no success. Current approaches to three-dimensional printing of self-standing and overhanging architectures have been achieved with the use of some form of supporting mould, secondary process or structure which could be either in the form of a viscous liquid or a solid structure to the coupling of lasers, temperature etc. Unfortunately, the use of such methodologies brings with them many issues and limitations, while destroying the concept of additive manufacturing. Note the author here defines additive manufacturing as a technology able to add materials when required during the fabrication of a 3D architecture without the need for external assistance or supports. These limitations in classical fabrication processes, restricts the use of advanced materials such as living biological cells to sensitive biomolecules to many others, for the forming of three-dimensional biological and non-biological architectures, whilst also increasing the costs and materials waste, which are required for acting as moulds, supports etc.

Three-Dimensional Additive Manufacturing of Artificial Oil Reservoir Rock Core Plugs for Core Flooding Experimental Tests.

Laboratory tests in which a fluid or combination of fluids that are injected into a core rock are designed to determine oil reservoir rock petrophysical properties, understand the mobility of fluid flow in the porous samples, and calibrate porous media fluid flow models. The core material is extracted from the oil reservoir. However, the manufacture of core plugs is challenging because of the complexity of extracting natural rocks from the reservoir and their morphological and atypical heterogeneity. In addition, core flooding tests are essentially destructive, making it impossible to achieve experimental repeatability by using identical cores. The use of 3D printing in digital rock physics has permitted the production and replication of synthetic rock samples with the morphological characteristics of natural rocks for core analysis and core flooding tests. This study proposes the 3D manufacture of artificial core plugs from microcomputed tomography of Berea sandstone. The digital samples were constructed using a digital particle packing approach by systematically manipulating rock textural parameters, such as the grain size and shape, cementation pattern, and sorting grain, making it possible to obtain a core plug that fulfills experimental requirements. Before the 3D printing of the sample, the flow distribution through the porous media structure was numerically simulated using the Lattice Boltzmann method to obtain the core plug samples' permeability and porosity. The core plug was digitally embedded within a core holder to generate a stereolithography file for 3D printing of the core flooding setup, which can be used directly in conventional experiments. The permeabilities of the 3D printed plugs were experimentally determined to permit a direct comparison to the numerical results and evaluate the utility of printed plugs for displacement experiments.

Mechanical Metamaterials Gyro-Structure Piezoelectric Nanogenerators for Energy Harvesting under Quasi-Static Excitations in Ocean Engineering.

In this study, we develop the mechanical metamaterial-enabled piezoelectric nanogenerators in the gyro-structure, which is reported as a novel green energy solution to generate electrical power under quasi-static excitations (i.e., <1 Hz) such as in the ocean environment. The plate-like mechanical metamaterials are designed with a hexagonal corrugation to improve their mechanical characteristics (i.e., effective bending stiffnesses), and the piezoelectric trips are bonded to the metaplates. The piezo-metaplates are placed in the sliding cells to obtain the post-buckling response for energy harvesting under low-frequency ocean motions. The corrugated mechanical metamaterials are fabricated using the three-dimensional additive manufacturing technique and are bonded with polyvinylidene fluoride strips, and the nanogenerator samples are investigated under the quasi-static loading. Theoretical and numerical models are developed to obtain the electrical power, and satisfactory agreements are observed. Optimization is conducted to maximize the generated electrical power with respect to the geometric consideration (i.e., changing the corrugation pattern of the mechanical metamaterials) and the material consideration (i.e., changing the mechanical metamaterials to anisotropic). In the end, we consider the piezoelectric nanogenerators as a potential green solution for the energy issues in other fields.

Biphasic Calcium Phosphate Biomaterials: Stem Cell-Derived Osteoinduction or In Vivo Osteoconduction? Novel Insights in Maxillary Sinus Augmentation by Advanced Imaging.

Maxillary sinus augmentation is often necessary prior to implantology procedure, in particular in cases of atrophic posterior maxilla. In this context, bone substitute biomaterials made of biphasic calcium phosphates, produced by three-dimensional additive manufacturing were shown to be highly biocompatible with an efficient osteoconductivity, especially when combined with cell-based tissue engineering. Thus, in the present research, osteoinduction and osteoconduction properties of biphasic calcium-phosphate constructs made by direct rapid prototyping and engineered with ovine-derived amniotic epithelial cells or amniotic fluid cells were evaluated. More in details, this preclinical study was performed using adult sheep targeted to receive scaffold alone (CTR), oAFSMC, or oAEC engineered constructs. The grafted sinuses were explanted at 90 days and a cross-linked experimental approach based on Synchrotron Radiation microCT and histology analysis was performed on the complete set of samples. The study, performed taking into account the distance from native surrounding bone, demonstrated that no significant differences occurred in bone regeneration between oAEC-, oAFMSC-cultured, and Ctr samples and that there was a predominant action of the osteoconduction versus the stem cells osteo-induction. Indeed, it was proven that the newly formed bone amount and distribution decreased from the side of contact scaffold/native bone toward the bulk of the scaffold itself, with almost constant values of morphometric descriptors in volumes more than 1 mm from the border.

Location-Specific Microstructure Characterization Within IN625 Additive Manufacturing Benchmark Test Artifacts

Additive manufacturing (AM) of alloys creates segregated microstructures with significant differences from those of traditional wrought alloys. Understanding how the local build conditions generate specific microstructures is essential for developing post-build heat treatments with the goal of producing parts with reliable and predictable properties. This research examines the position- and orientation-dependent microstructures within IN625 Additive Manufacturing Benchmark Test specimens, including three-dimensional AM builds and individual laser traces on bare metal plates. Detailed characterizations of the solidification microstructures, compositional heterogeneities, grain structures and orientations, and melt pool geometries are described.

The Adoption of Three-Dimensional Additive Manufacturing from Biomedical Material Design to 3D Organ Printing

Three-dimensional (3D) bioprinting promises to change future lifestyle and the way we think about aging, the field of medicine, and the way clinicians treat ailing patients. In this brief review, we attempt to give a glimpse into how recent developments in 3D bioprinting are going to impact vast research ranging from complex and functional organ transplant to future toxicology studies and printed organ-like 3D spheroids. The techniques were successfully applied to reconstructed complex 3D functional tissue for implantation, application-based high-throughput (HTP) platforms for absorption, distribution, metabolism, and excretion (ADME) profiling to understand the cellular basis of toxicity. We also provide an overview of merits/demerits of various bioprinting techniques and the physicochemical basis of bioink for tissue engineering. We briefly discuss the importance of universal bioink technology, and of time as the fourth dimension. Some examples of bioprinted tissue are shown, followed by a brief discussion on future biomedical applications.

Bioactive composites based on double network approach with tailored mechanical, physico‐chemical, and biological features

Hyaluronic acid (HA)-based hydrogels are one of the most promising naturally derived biomaterials for tissue engineering applications, as they can play an important role in many key cellular processes. In this study, HA was chemically functionalized with photo-cross-linkable motifs by reacting with methacrylic anhydride (MA) to obtain methacrylated hyaluronic acid (MeHA). A range of MA/HA molar ratios was used to obtain different degrees of substitution (DS) ranging from 3.5% to 74.5%, as showed by nuclear magnetic resonance and attenuated total reflection spectroscopy. By fine tuning the DS, the chemical reaction parameters, and the polymer concentration, it was demonstrated the possibility to tailor their mechanical features. Double network (DN) hydrogels were prepared through the synergic use of MeHA and polyethylene glycole diacrylate (PEGDA). To improve the biological properties of DN hydrogels, bioactive solid signals such as hydroxyapatite nanoparticles (HAp) prepared by sol-gel approach were used in combination with DN hydrogels to obtain an advanced composite material with dual function in terms of mechanical and biological support for soft/hard tissue formation. The results highlighted that composite-DN hydrogels showed a 10-time increase of the storage modulus, if compared to neat MeHA, and an early alkaline phosphatase expression from human mesenchymal stem cells in basal medium. This work can be considered a first systematic approach for the designing of photo-cross-linkable hydrogels, based on a combination of natural/synthetic polymers and HAp, that could be applied in three-dimensional additive manufacturing techniques such as stereolithography. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 3079-3089, 2018.

Additive Manufacturing of Honeybee-Inspired Microneedle for Easy Skin Insertion and Difficult Removal.

With natural evolution, honeybee stinger with microbarbs can easily penetrate and trap in the skin of hostile animals to inject venom for self-defense. We proposed a novel three-dimensional additive manufacturing method, namely magnetorheological drawing lithography, to efficiently fabricate a bioinspired microneedle imitating a honeybee stinger. Under the assistance of an external magnetic field, a parent microneedle was directly drawn on the pillar tip, and tilted microbarbs were subsequently formed on the four sides of the parent microneedle. Compared with the barbless microneedle, the microstructured barbs enable the bioinspired microneedle for easy skin insertion and difficult removal. The extraction-penetration force ratio of the bioinspired microneedle was triple that of the barbless microneedle. The stress concentration at the barbs helps to reduce the insertion force of the bioinspired microneedle by minimizing the frictional force, whereas it increases the adhesion force by interlocking the barbs in the tissue during retraction. Such finds may provide an inspiration for further design of barbed microtip-based microneedles for tissue adhesion, transdermal drug delivery, biosignal recording, and so on.

3次元積層造形のはじまり

3次元積層造形のはじまり

Lead-free piezoelectric composites produced by three-dimensional additive manufacturing

Lead-free piezoelectric composites produced by three-dimensional additive manufacturing

Fabrication of a biomimetic elastic intervertebral disk scaffold using additive manufacturing

A custom-designed three-dimensional additive manufacturing device was developed to fabricate scaffolds for intervertebral disk (IVD) regeneration. This technique integrated a computer with a device capable of 3D movement allowing for precise motion and control over the polymer scaffold resolution. IVD scaffold structures were designed using computer-aided design to resemble the natural IVD structure. Degradable polyurethane (PU) was used as an elastic scaffold construct to mimic the elastic nature of the native IVD tissue and was deposited at a controlled rate using ultra-fine micropipettes connected to a syringe pump. The elastic PU was extruded directly onto a collecting substrate placed on a freezing stage. The three-dimensional movement of the computer-controlled device combined with the freezing stage enabled precise control of polymer deposition using extrusion. The addition of the freezing stage increased the polymer solution viscosity and hardened the polymer solution as it was extruded out of the micropipette tip. This technique created scaffolds with excellent control over macro- and micro-structure to influence cell behavior, specifically for cell adhesion, proliferation, and alignment. Concentric lamellae were printed at a high resolution to mimic the native shape and structure of the IVD. Seeded cells aligned along the concentric lamellae and acquired cell morphology similar to native tissue in the outer portion of the IVD. The fabricated scaffolds exhibited elastic behavior during compressive and shear testing, proving that the scaffolds could support loads with proper fatigue resistance without permanent deformation. Additionally, the mechanical properties of the scaffolds were comparable to those of native IVD tissue.