Advances In 3D Printing Research Articles

A shear center demonstration model using 3D-printing

Locating the shear, or flexural, center of non-symmetric cross-sectional beams is a key element in the teaching of structural mechanics. That is, establishing the point on the plane of the cross-section where an applied load, generating a bending moment about a principal axis, results in uni-directional deflection, and no twisting. For example, in aerospace structures it is particularly important to assess the propensity of an airfoil section profile to resist bending and torsion under the action of aerodynamic forces. Cross-sections made of thin-walls, whether of open or closed form are of special practical importance and form the basis of the material in this paper. The advent of 3D-printing allows the development of tactile demonstration models based on non-trivial geometry and direct observation.

Thermal and Environmental Benefits of 3D Printing on Building Construction

The main goal of this work is the analysis of the thermal and environmental benefits of 3D printing on building construction. Present literature reports a considerable number of benefits for 3D printing, namely reduction of material use, lower operational costs and time saving. Authors also mention design freedom, higher efficiency, productivity and quality. This work presents the most important advances in 3D printing in civil engineering, specifically, a critical review of the thermal and environmental benefits of 3D printing on building construction. The limitations of construction 3D printing with focus on large-scale applications, technology costs, mix development and optimisation and thermal behaviour will be, also, defined.

Design, fabrication and implementation of a high-performance compliant nanopositioner via 3D printing with continuous fiber-reinforced composite

Nanopositioning systems have been widely applied in scientific and emerging industrial applications. With simplicity in design and operation, flexure bearings with spatial constraints and voice coil based nano-actuators are considered in designing compliant compact nanopositioning systems. To achieve nano-metric positioning quality, monolithic fabrication of the positioner is preferred, which calls for 3D printing fabrication. However, conventional plastic material-based 3D printing suffers from low mechanical performances, and it is challenging to monolithically fabricate 3D compliant mechanisms with high mechanical performances. Here, we study the fabrication of continuous carbon fiber reinforced composites by 3D printing of the double parallelogram flexure beam structures for spatial constrained nanopositioner with enhanced vertical stiffness. Also, with the consideration of the beam structure design, the process parameters for embedding the carbon fibers are optimized to enhance the beam strengths. Experimental results demonstrate a significant performance improvement with the composite based nanopositioner in both stiffness and natural frequency, and its positioning resolution of 30 nm is achieved. The result of this study will serve as the building block to apply advanced 3D printing of composite structure for precision engineering in the presence of more complex spatial structures.

3D Printing for Solid-State Energy Storage.

Ever-growing demand to develop satisfactory electrochemical devices has driven cutting-edge research in designing and manufacturing reliable solid-state electrochemical energy storage devices (EESDs). 3D printing, a precise and programmable layer-by-layer manufacturing technology, has drawn substantial attention to build advanced solid-state EESDs and unveil intrinsic charge storage mechanisms. It provides brand-new opportunities as well as some challenges in the field of solid-state energy storage. This review focuses on the topic of 3D printing for solid-state energy storage, which bridges the gap between advanced manufacturing and future EESDs. It starts from a brief introduction followed by an emphasis on 3D printing principles, where basic features of 3D printing and key issues for solid-state energy storage are both reviewed. Recent advances in 3D printed solid-state EESDs including solid-state batteries and solid-state supercapacitors are then summarized. Conclusions and perspectives are also provided regarding the further development of 3D printed solid-state EESDs. It can be expected that advanced 3D printing will significantly promote future evolution of solid-state EESDs.

Fused deposition modelling: Current status, methodology, applications and future prospects

Fused deposition modelling (FDM) is an advanced 3D printing technique for the manufacture of plastic materials. The ease of use, prototyping accuracy and low cost makes it a widely used additive manufacturing technique. FDM creates 3D structures through the layer-by-layer melt-extrusion of a plastic filament. The production of a printed structure involves the generation of a digital design of the model by 3D design software and its execution by the printer until the complete model is reproduced. This review presents the current status of FDM, how to handle and operate FDM printers, industry standards of printing, the types of filaments that can be used, the post-processing treatments, advantages, and limitations as well as an overview of the increasing application fields of FDM technology. The application areas of FDM are endless, including biomedicine, construction, automotive, aerospace, acoustics, textiles, and occupational therapy amongst others. Even during the current Coronavirus disease (COVID-19) pandemic, FDM has helped to fabricate face masks, ventilators and respiratory systems, respiratory valves, and nasopharyngeal swabs for COVID-19 diagnosis. FDM 3D and 4D printing can produce polymeric and composite structures of various designs, and compositions in a range of materials according to the desired application. The review concludes by discussing the future prospects for FDM.

Parametric and Metallurgical Investigation of Modified 3D AM 80 HD Steel for Wire and Arc Additive Manufacturing

Wire and arc additive manufacturing (WAAM) is an advanced 3D printing method for metallic materials on the foundation of traditional arc welding processes. WAAM is regarded as a proper way to manufacture large-dimensional metallic parts with the combination of high deposition rate and low cost. In this research, a specifically designed and manufactured low carbon high strength steel (Grade 3D AM 80 HD) wire, equivalent to a composition of AWS ER 110S-1 wire, was deposited using WAAM to print a muti-beads wall aiming to explore its feasibility for heavily loaded marine applications. A parametric investigation was proceeded to find the optimal deposition voltage and overlap ratio. A vertical position compensation method was adopted to optimize the step-up distance for welding torch between neighboring layers. Microstructure of the deposited component was characterized and also indicated by Thermal-Calc Software, followed by the measurement of hardness and prediction of tensile strength. Furthermore, a comparison of tensile strength of the WAAMed 3D AM 80 HD wall, 3D AM 80 HD wire, AWS ER 110S-1 wire, and a WAAMed wall produced by wire manufacturer (Voestalpine Böhler Welding Corporation) was conducted.

CVD Synthesis of 3D-Shaped 3D Graphene Using a 3D-Printed Nickel-PLGA Catalyst Precursor.

Earlier, various attempts to develop graphene structures using chemical and nonchemical routes were reported. Being efficient, scalable, and repeatable, 3D printing of graphene-based polymer inks and aerogels seems attractive; however, the produced structures highly rely on a binder or an ice support to stay intact. The presence of a binder or graphene oxide hinders the translation of the excellent graphene properties to the 3D structure. In this communication, we report our efforts to synthesize a 3D-shaped 3D graphene (3D2G) with good quality, desirable shape, and structure control by combining 3D printing with the atmospheric pressure chemical vapor deposition (CVD) process. Direct ink writing has been used in this work as a 3D-printing technique to print nickel powder–PLGA slurry into various shapes. The latter has been employed as a catalyst for graphene growth via CVD. Porous 3D2G with high purity was obtained after etching out the nickel substrate. The conducted micro CT and 2D Raman study of pristine 3D2G revealed important features of this new material. The interconnected porous nature of the obtained 3D2G combined with its good electrical conductivity (about 17 S/cm) and promising electrochemical properties invites applications for energy storage electrodes, where fast electron transfer and intimate contact with the active material and with the electrolyte are critically important. By changing the printing design, one can manipulate the electrical, electrochemical, and mechanical properties, including the structural porosity, without any requirement for additional doping or chemical postprocessing. The obtained binder-free 3D2G showed a very good thermal stability, tested by thermo-gravimetric analysis in air up to 500 °C. This work brings together two advanced manufacturing approaches, CVD and 3D printing, thus enabling the synthesis of high-quality, binder-free 3D2G structures with a tailored design that appeared to be suitable for multiple applications.

3D Printed Biodegradable Polyurethaneurea Elastomer Recapitulates Skeletal Muscle Structure and Function.

Effective skeletal muscle tissue engineering relies on control over the scaffold architecture for providing muscle cells with the required directionality, together with a mechanical property match with the surrounding tissue. Although recent advances in 3D printing fulfill the first requirement, the available synthetic polymers either are too rigid or show unfavorable surface and degradation profiles for the latter. In addition, natural polymers that are generally used as hydrogels lack the required mechanical stability to withstand the forces exerted during muscle contraction. Therefore, one of the most important challenges in the 3D printing of soft and elastic tissues such as skeletal muscle is the limitation of the availability of elastic, durable, and biodegradable biomaterials. Herein, we have synthesized novel, biocompatible and biodegradable, elastomeric, segmented polyurethane and polyurethaneurea (TPU) copolymers which are amenable for 3D printing and show high elasticity, low modulus, controlled biodegradability, and improved wettability, compared to conventional polycaprolactone (PCL) and PCL-based TPUs. The degradation profile of the 3D printed TPU scaffold was in line with the potential tissue integration and scaffold replacement process. Even though TPU attracts macrophages in 2D configuration, its 3D printed form showed limited activated macrophage adhesion and induced muscle-like structure formation by C2C12 mouse myoblasts in vitro, while resulting in a significant increase in muscle regeneration in vivo in a tibialis anterior defect in a rat model. Effective muscle regeneration was confirmed with immunohistochemical assessment as well as evaluation of electrical activity produced by regenerated muscle by EMG analysis and its force generation via a custom-made force transducer. Micro-CT evaluation also revealed production of more muscle-like structures in the case of implantation of cell-laden 3D printed scaffolds. These results demonstrate that matching the tissue properties for a given application via use of tailor-made polymers can substantially contribute to the regenerative outcomes of 3D printed tissue engineering scaffolds.

1208 Silent Sinus Syndrome: Systematic Literature Review and Report of Case Treated with A Customised PEEK Orbital Floor Implant

Abstract Aim Silent sinus syndrome is a rare condition characterised by progressive, painless enophthalmos with subsequent development of hypoglobus due to orbital floor resorption. It is caused by hypoplasia of the ipsilateral maxillary sinus due to atelectasis. It may be associated with previous orbital floor surgery or trauma or may be idiopathic. We describe the case of a 33-year-old female treated with a customised orbital floor implant, and a review of the condition from available literature. Method A total of 53 patients with a diagnosis of silent sinus syndrome reported in 7 different papers from 2003-2020 were compared in age, presenting signs and symptoms, radiographic findings and the types of treatment provided. Results The patients ranged from ages 19 to 91, with an average age of 45.1 years, and a male to female split of 29:24. The most common presenting sign was progressive unilateral enophthalmos, usually in the absence of any ocular symptoms. Treatments included endoscopic maxillary antroscopy, orbital floor repair (prefabricated or customised) and septoplasty. Conclusions Silent sinus syndrome typically presents with unilateral enophthalmos which is often painless and not associated with any visual disturbance. It possesses characteristic clinical and radiographic signs. The management of choice is surgical and does not tend to recur in the years immediately following resolving treatment. Since the advent of 3D printing, accurate customised orbital plates can now be designed to correct the hypoglobus which is a major aesthetic component when it presents in this condition.

High Resolution and Labeling Free Studying the 3D Microstructure of the Pars Tensa-Annulus Unit of Mice.

Hearing loss is a serious illness affecting people’s normal life enormously. The acoustic properties of a tympanic membrane play an important role in hearing, and highly depend on its geometry, composition, microstructure and connection to the surrounding annulus. While the conical geometry of the tympanic membrane is critical to the sound propagation in the auditory system, it presents significant challenges to the study of the 3D microstructure of the tympanic membrane using traditional 2D imaging techniques. To date, most of our knowledge about the 3D microstructure and composition of tympanic membranes is built from 2D microscopic studies, which precludes an accurate understanding of the 3D microstructure, acoustic behaviors and biology of the tissue. Although the tympanic membrane has been reported to contain elastic fibers, the morphological characteristic of the elastic fibers and the spatial arrangement of the elastic fibers with the predominant collagen fibers have not been shown in images. We have developed a 3D imaging technique for the three-dimensional examination of the microstructure of the full thickness of the tympanic membranes in mice without requiring tissue dehydration and stain. We have also used this imaging technique to study the 3D arrangement of the collagen and elastic fibrillar network with the capillaries and cells in the pars tensa-annulus unit at a status close to the native. The most striking findings in the study are the discovery of the 3D form of the elastic and collagen network, and the close spatial relationships between the elastic fibers and the elongated fibroblasts in the tympanic membranes. The 3D imaging technique has enabled to show the 3D waveform contour of the collagen and elastic scaffold in the conical tympanic membrane. Given the close relationship among the acoustic properties, composition, 3D microstructure and geometry of tympanic membranes, the findings may advance the understanding of the structure—acoustic functionality of the tympanic membrane. The knowledge will also be very helpful in the development of advanced cellular therapeutic technologies and 3D printing techniques to restore damaged tympanic membranes to a status close to the native.

The Application of Cartilage Tissue Engineering with Cell-Laden Hydrogel in Plastic Surgery: A Systematic Review.

As a contour-supporting material, the cartilage has a significant application value in plastic surgery. Since the development of hydrogel scaffolds with sufficient biomechanical strength and high biocompatibility, cell-laden hydrogels have been widely studied for application in cartilage bioengineering. This systematic review summarizes the latest research on engineered cartilage constructed using cell-laden hydrogel scaffolds in plastic surgery. A systematic review was performed by searching the PubMed and Web of Science databases using selected keywords and Medical Subject Headings search terms. Forty-two studies were identified based on the search criteria. After full-text screening for inclusion and exclusion criteria, 18 studies were included. Data collected from each study included culturing form, seed cell types and sources, concentration of cells and gels, scaffold materials and bio-printing structures, and biomechanical properties of cartilage constructs. These cell-laden hydrogel scaffolds were reported to show some feasibility of cartilage engineering, including better cell proliferation, enhanced deposition of glycosaminoglycans and collagen type II in the extracellular matrix, and better biomechanical properties close to the natural state. Cell-laden hydrogels have been widely used in cartilage bioengineering research. Through 3-dimensional (3D) printing, the cell-laden hydrogel can form a bionic contour structure. Extracellular matrix expression was observed in vivo and in vitro, and the elastic modulus was reported to be similar to that of natural cartilage. The future direction of cartilage tissue engineering in plastic surgery involves the use of novel hydrogel materials and more advanced 3D printing technology combined with biochemistry and biomechanical stimulation.

Taking internally wetted capillary electrospray emitters to the sub-ten-micrometer scale with 3D microlithography

Electrospray emitters are an obvious choice for miniaturized thrusters for a variety of applications on small satellites (e. g., CubeSats), as well as for other micropropulsion purposes. They are inherently small and require a relatively low electric power for operation, and therefore, they fulfill the requirements imposed due to the small volume of CubeSats. Electrospray emitters of the internally wetted capillary type were fabricated by 3D microlithography in the SU-8 photopolymer down to capillary diameters of about 10 μm. Thus, the emitters are an order of magnitude smaller in lateral dimensions than those fabricated by advanced 3D printing methods and still half an order of magnitude smaller than those made by planar photolithography in SU-8. Fabrication methods and process parameters are presented. Furthermore, the preliminary results of the electric characterization of the emission behavior are shown. The experiments show promising results regarding the fabrication quality and extraction behavior.

3D Printing in Spine Surgery: Current and Future Applications

The revolutionary technology of 3D printing has gained traction in the medical field in recent years; spine surgery has in particular seen major advances in 3D printing. The applications of this technology have grown from utilizing 3D models to enhance patient education to patient specific, highly detailed intraoperative anatomical molds. However, obstacles remain that prevent the widespread utilization of 3D printing in spine surgery such as cost, time consumption, lack of long-term data, and regulation by the US FDA. Despite these obstacles, it is evident that 3D printing will be utilized to optimize preoperative, intraoperative, and postoperative care of patients with spine deformity. The purpose of this review is to establish the applications of 3D printing for spine surgery.

Recent Advancements in 3D Printing and Bioprinting Methods for Cardiovascular Tissue Engineering.

Recent decades have seen a plethora of regenerating new tissues in order to treat a multitude of cardiovascular diseases. Autografts, xenografts and bioengineered extracellular matrices have been employed in this endeavor. However, current limitations of xenografts and exogenous scaffolds to acquire sustainable cell viability, anti-inflammatory and non-cytotoxic effects with anti-thrombogenic properties underline the requirement for alternative bioengineered scaffolds. Herein, we sought to encompass the methods of biofabricated scaffolds via 3D printing and bioprinting, the biomaterials and bioinks recruited to create biomimicked tissues of cardiac valves and vascular networks. Experimental and computational designing approaches have also been included. Moreover, the in vivo applications of the latest studies on the treatment of cardiovascular diseases have been compiled and rigorously discussed.

3D Printing for Experiments in Petrophysics, Rock Physics, and Rock Mechanics: A Review

Summary Geoscientific and engineering experiments in petrophysics, rock physics, and rock mechanics depend on multiple, costly, and sometimes rare samples used to characterize the properties of natural rocks. Testing these samples helps in modeling various hydrocarbon recovery and stimulation scenarios, as well as understanding the fluid-rock interactions in the subsurface under various pressure and temperature conditions. Over the last decade, 3D printing has matured to become a more commonly available tool to enable repeatable experiments with controllable materials and pore system geometries to investigate petrophysical, geomechanical, and geophysical properties of porous rocks. This review introduces the development, characteristics, and capabilities of 3D printing technology that are specifically used in research. Applications in the realm of petrophysics highlight the issues of replicating the pore network geometry and subsurface physics, aiming at understanding fluid flow in porous media problems. Using 3D-printed models in rock mechanics experiments focuses on generating comparable geomechanical properties and reproducing fractures, joint surfaces, and other rock structures, whereas in rock physics, geophysical forward modeling is highlighted to take advantage of 3D printing technology. By summarizing the recent advances in 3D printing as applied to petrophysics, rock physics, and rock mechanics, this review paper presents the current state of the art and the challenges in scale, cost, time, and materials, as well as the directions for advancing this frontier discipline to answer various fundamental questions regarding porous media research using 3D printing technology.

Review of Materials and Fabrication Methods for Flexible Nano and Micro-Scale Physical and Chemical Property Sensors

The use of flexible sensors has tripled over the last decade due to the increased demand in various fields including health monitoring, food packaging, electronic skins and soft robotics. Flexible sensors have the ability to be bent and stretched during use and can still maintain their electrical and mechanical properties. This gives them an advantage over rigid sensors that lose their sensitivity when subject to bending. Advancements in 3D printing have enabled the development of tailored flexible sensors. Various additive manufacturing methods are being used to develop these sensors including inkjet printing, aerosol jet printing, fused deposition modelling, direct ink writing, selective laser melting and others. Hydrogels have gained much attention in the literature due to their self-healing and shape transforming. Self-healing enables the sensor to recover from damages such as cracks and cuts incurred during use, and this enables the sensor to have a longer operating life and stability. Various polymers are used as substrates on which the sensing material is placed. Polymers including polydimethylsiloxane, Poly(N-isopropylacrylamide) and polyvinyl acetate are extensively used in flexible sensors. The most widely used nanomaterials in flexible sensors are carbon and silver due to their excellent electrical properties. This review gives an overview of various types of flexible sensors (including temperature, pressure and chemical sensors), paying particular attention to the application areas and the corresponding characteristics/properties of interest required for such. Current advances/trends in the field including 3D printing, novel nanomaterials and responsive polymers, and self-healable sensors and wearables will also be discussed in more detail.

A Three-Dimensional Printed Foot Orthosis for Flexible Flatfoot: An Exploratory Biomechanical Study on Arch Support Reinforcement and Undercut.

The advancement of 3D printing and scanning technology enables the digitalization and customization of foot orthosis with better accuracy. However, customized insoles require rectification to direct control and/or correct foot deformity, particularly flatfoot. In this exploratory study, we aimed at two design rectification features (arch stiffness and arch height) using three sets of customized 3D-printed arch support insoles (R+U+, R+U−, and R−U+). The arch support stiffness could be with or without reinforcement (R+/−) and the arch height may or may not have an additional elevation, undercutting (U+/−), which were compared to the control (no insole). Ten collegiate participants (four males and six females) with flexible flatfoot were recruited for gait analysis on foot kinematics, vertical ground reaction force, and plantar pressure parameters. A randomized crossover trial was conducted on the four conditions and analyzed using the Friedman test with pairwise Wilcoxon signed-rank test. Compared to the control, there were significant increases in peak ankle dorsiflexion and peak pressure at the medial midfoot region, accompanied by a significant reduction in peak pressure at the hindfoot region for the insole conditions. In addition, the insoles tended to control hindfoot eversion and forefoot abduction though the effects were not significant. An insole with stronger support features (R+U+) did not necessarily produce more favorable outcomes, probably due to over-cutting or impingement. The outcome of this study provides additional data to assist the design rectification process. Future studies should consider a larger sample size with stratified flatfoot features and covariating ankle flexibility while incorporating more design features, particularly medial insole postings.

TRANSITION FROM TRADITIONAL COB CONSTRUCTION TO 3D PRINTING OF CLAY HOMES

ABSTRACT 3D printing of cementitious material can provide an affordable, sustainable, and optimized approach for the construction of homes, without compromising quality or craftsmanship. While most of the current research and development efforts in this field are focused on cement-based concrete printing, this paper focuses on the current state-of-the-art literature review of designing and developing a sustainable clay-based mixture design that mainly includes clay, sand, straw, lime, and water. The goal of this paper is to bridge the gap between typical traditional earth construction, specifically cob construction, and emerging 3D printing of cementitious materials. The specific objective of this paper is to offer some possible changes in the typical cob mixture so that it can be used for 3D printing of clay-based mixtures with sufficient flowability, buildability, strength, and open time (i.e., the time period between printing of one layer and printing of another layer deposited on a layer below). The paper describes typical clay-based mixtures and their traditional process and then specifies the challenges in going from traditional cob construction to advanced computer-controlled robotic 3D printing.

A novel bio-inspired hydrogel-based lattice structure to mechanically mimic human annulus fibrosus: A finite element study

Intervertebral disc hernia and dysfunctions are the most common health problems that affect humans. For this reason, the need of disc prosthetics, and especially annulus fibrosus replacements, is becoming increasingly mandatory and urgent. In the present paper, we present a novel bio-inspired hydrogel-based replacement system with rational mechanically mimetic designs of human annulus fibrosus. The new system consists of hydrogel-based lattice structure with octagonal cells separated by polylactide fibers reinforced hydrogel-based sheets. The mechanics of the new designs may be rationally controlled by tailoring microstructure, in terms of polylactide fibers orientation and hydrogel intrinsic viscosity, and mesostructure in terms of cell walls/sheets thickness. The new designs are successfully compared to the natural annulus fibrosus mechanics in terms of nonlinear stiffness and transversal behavior while considering regional dependency. The impressive biomimetic capabilities of the proposed hydrogel-based lattice structure allow foreseeing the possibility of designing personalized disc prosthetics by advanced 3D printing technologies.

Bioengineering approaches to treat the failing heart: from cell biology to 3D printing.

Successfully engineering a functional, human, myocardial pump would represent a therapeutic alternative for the millions of patients with end-stage heart disease and provide an alternative to animal-based preclinical models. Although the field of cardiac tissue engineering has made tremendous advances, major challenges remain, which, if properly resolved, might allow the clinical implementation of engineered, functional, complex 3D structures in the future. In this Review, we provide an overview of state-of-the-art studies, challenges that have not yet been overcome and perspectives on cardiac tissue engineering. We begin with the most clinically relevant cell sources used in this field and discuss the use of topological, biophysical and metabolic stimuli to obtain mature phenotypes of cardiomyocytes, particularly in relation to organized cytoskeletal and contractile intracellular structures. We then move from the cellular level to engineering planar cardiac patches and discuss the need for proper vascularization and the main strategies for obtaining it. Finally, we provide an overview of several different approaches for the engineering of volumetric organs and organ parts - from whole-heart decellularization and recellularization to advanced 3D printing technologies.