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[Display omitted] • Development of a tool, the feed force tester, to determine printing parameters for different pharmaceutical formulations. • Transfer of feed force data to the actual printing process to optimize printing speed and nozzle temperature. • X-ray microtomography and melt rheology were used to explain the interaction between printing speed and temperature. Fused Deposition Modeling is a suitable technique for the production of personalized solid oral dosage forms. For widespread application, it is necessary to be able to print a wide range of different formulations to address individual therapeutic needs. Due to the complexity of formulation composition (e.g., due to different compounds, excipients for enhancement of release and mechanical properties) and limited mechanical understanding, determination of suitable printing parameters is challenging. To address this challenge, we have developed a feed force tester using a Texture Analyser setup that mimics the actual printing process. Feed force data were compared to the mass of tablets printed from technical materials as well as pharmaceutical filaments containing ketoconazole at high drug loads of 20% and 40% and polyvinyl alcohol. By determining a feed force limit for the 3D printer from feed force data of several formulations printed, it was possible to specify the operable printing range, where printing is reproducible and printed mass corresponds the target mass. Based on these results, rational optimization of the printing process in terms of speed, time and temperature for different materials and formulations is possible. [ABSTRACT FROM AUTHOR]

The objective of this investigation is to study the printing parameter requirements for sustainable 3D printable geopolymer materials. Side streams of the paper, mining, and construction industries were applied as geopolymer raw materials. The effect of printing parameters in terms of buildability, mixability, extrudability, curing, Al-to-Si ratio, and waste materials utilisation on the fresh and hardened state of the materials was studied. The material performance of a fresh geopolymer was measured using setting time and shape stability tests. Standardised test techniques were applied in the testing of the hardened material properties of compressive and flexural strength. The majority of developed suitable 3D printable geopolymers comprised 56–58% recycled material. Heating was used to improve the buildability and setting of the material significantly. A reactive recyclable material content of greater than 20% caused the strength and material workability to decrease. A curing time of 7–28 days increased the compressive strength but decreased the flexural strength. The layers in the test samples exhibited decreased and increased strength, respectively, in compressive and flexural strength tests. Geopolymer development was found to be a compromise between different strength values and recyclable material contents. By focusing on specialised and complex-shape products, 3D printing of geopolymers can compete with traditional manufacturing in limited markets. [ABSTRACT FROM AUTHOR]

The work deals with the investigation of the variation of the selected 3D printing process properties that originate from the choice of a slicer. Specifically, the main aim of the present study was to assess the induced changes of the kinematic and geometric properties considered by the slicer for the printing process making use of the G-code readings. The paper provides adequate definitions and formulas required to characterize the slicer's configuration. Next, the selected cases of the process parameters' changes were studied, primarily taking into account varying layer height and infill. The authors performed a detailed analysis regarding the geometric implications at the mesoscale due to the slicer's settings. Appropriate modifications of the slicer's properties were also proposed and verified, making it possible to match the geometric and kinematic characteristics of the printed part. [ABSTRACT FROM AUTHOR]

As one of the fastest-growing additive manufacturing (AM) technologies, fused deposition modelling (FDM) shows great potential in printing natural fibre-reinforced composites (NFRC). However, several challenges, such as low mechanical properties and difficulty in printing, need to be overcome. Therefore, the effort to improve the NFRC for use in AM has been accelerating in recent years. This review attempts to summarise the current approaches of using NFRC as a feeder for AM. The effects of fibre treatments, composite preparation methods and addition of compatibilizer agents were analysed and discussed. Additionally, current methods of producing feeders from NFRCs were reviewed and discussed. Mechanical property of printed part was also dependent on the printing parameters, and thus the effects of printing temperature, layer height, infill and raster angle were discussed, and the best parameters reported by other researchers were identified. Following that, an overview of the mechanical properties of these composites as reported by various researchers was provided. Next, the use of optimisation techniques for NFRCs was discussed and analysed. Lastly, the review provided a critical discussion on the overall topic, identified all research gaps present in the use of NFRC for AM processes, and to overcome future challenges. [ABSTRACT FROM AUTHOR]

Technology evolution and wide research attention on 3D printing efficiency and processes have given the prompt need to reach an understanding about each technique's prowess to deliver superior quality levels whilst showing an economical and process viability to become mainstream. Studies in the field have struggled to predict the singularities that arise during most Fused Deposition Modeling (FDM) practices; therefore, diverse individual description of the parameters have been performed, but a relationship study between them has not yet assessed. The proposed study lays the main defects caused by a selection of printing parameters which might vary layer slicing, then influencing the defect rate. Subsequently, the chosen technique for optimization is presented, with evidence of its application viability that suggests that a quality advance would be gathered with such. The results would help in making the FDM process become a reliable process that could also be used for industry manufacturing besides prototyping purposes. [ABSTRACT FROM AUTHOR]

Microneedles (MNs) represent the concept of attractive, minimally invasive puncture devices of micron-sized dimensions that penetrate the skin painlessly and thus facilitate the transdermal administration of a wide range of active substances. MNs have been manufactured by a variety of production technologies, from a range of materials, but most of these manufacturing methods are time-consuming and expensive for screening new designs and making any modifications. Additive manufacturing (AM) has become one of the most revolutionary tools in the pharmaceutical field, with its unique ability to manufacture personalized dosage forms and patient-specific medical devices such as MNs. This review aims to summarize various 3D printing technologies that can produce MNs from digital models in a single step, including a survey on their benefits and drawbacks. In addition, this paper highlights current research in the field of 3D printed MN-assisted transdermal drug delivery systems and analyzes parameters affecting the mechanical properties of 3D printed MNs. The current regulatory framework associated with 3D printed MNs as well as different methods for the analysis and evaluation of 3D printed MN properties are outlined. [ABSTRACT FROM AUTHOR]

Fused deposition modeling (FDM) is one of the most often-used technologies in additive manufacturing. Several materials are used with this technology, such as poly(lactic acid) (PLA), which is most commonly applied. The mechanical properties of 3D-printed parts depend on the process parameters. This is why, in this study, three-point bending tests were carried out to characterize the influence of build orientation, layer thickness, printing temperature and printing speed on the mechanical properties of PLA samples. Not only the process parameters may affect the mechanical properties, but heat after-treatment also has an influence on them. For this reason, additional samples were printed with optimal process parameters and characterized after pure heat treatment as well as after deformation at a temperature above the glass transition temperature, cooling with applied deformation, and subsequent recovery under heat treatment. These findings are planned to be used in a future study on finger orthoses that could either be printed according to shape or in a flat shape and afterwards heated and bent around the finger. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) is driving a change in the industry not only regarding prototyping but due to the ease of including printed parts in final designs. Engineers and designers can go deeper into optimization and improvements of their designs without drawbacks of long manufacturing times. However, some drawbacks such as the limited available materials or uncertainty about mechanical properties and anisotropic behavior of 3D printed parts prevent use in large-scale production. To gain knowledge and confidence about printed materials it is necessary to know how they behave under different stress states and strain-rate regimes, and how some of the printing parameters may affect them. The present work proposes an experimental methodology framework to study and characterize materials printed by stereolithography (SLA) to clarify certain aspects that must be taken into account to broaden the use of this kind of material. To this end, tensile and compression tests at different strain rates were carried out. To study the influence of certain printing parameters on the printed material behavior, samples with different printing angles (θ = [0–90]) and different printing resolution (layer height of 50 and 100 µm) were tested. In addition, the effects of curing time and temperature were also studied. The testing specimens were manufactured in the non-professional SLA machine Form 2 from Formlabs® using resin called Durable. Nevertheless, the proposed experimental methodology could be extended to any other resin. [ABSTRACT FROM AUTHOR]

Scaffold micro-topological structure plays an important role in the regulation of cell behavior in bone tissue engineering. This paper investigated the effect of 3D printing parameters on the scaffold micro-topological structure and its subsequent cell behaviors. By setting of different 3D printing parameters, i.e. , the 3D printing laser power, the scanning interval and the thickness of sliced layers, the highest resolution up to 20 μm can be precisely fabricated. Scaffolds' characterization results indicated that the laser power affected the forming quality of melt tracks, the scanning interval distance determined the size of regularly arranged pores, and the thickness of sliced layers affected the morphological and structural characteristics. By regulating of these printing parameters, customized porous Ti6Al4V scaffold with varied hierarchical micro-topological structure can be obtained. In vitro cell culturing results showed that the regular porous micro-topological structure of scaffolds with the aperture close to cell size was more suitable for cell proliferation and adhesion. The overall distribution of cells on regular porous scaffolds was similar to the orderly arrangement of cultivated crops in the field. The findings suggested that customization of the scaffold provided an effective way to regulate cellular behavior and biological properties. Scaffold hierarchical microstructures were inspired by the orderly arrangement of cultivated crops in the field, which can be fabricated by adjusting selective laser melting. In 3D printed porous Ti6Al4V scaffolds, regularly arranged macrostructures promote bone tissue ingrowth, and micro-topological structures regulate cell behaviors. Unlabelled Image • Scaffold hierarchical microstructures are inspired by the orderly arrangement of cultivated crops in the field. • Scaffold hierarchical microstructures were customized fabricated by selective laser melting. • Regularly arranged macrostructures in 3D printed porous Ti6Al4V scaffolds promote bone tissue ingrowth. • Micro-topological structures in porous Ti6Al4V scaffolds regulate cell behaviors. [ABSTRACT FROM AUTHOR]

• Basic principles for 3D printers used in pharmaceutical formulations. • The effect of 3D printing processing parameters on the formulation properties. • The effect of formulation design on the formulation properties. • Applications of 3D printing in formulating drug-loaded structures. In the recent decade, three-dimensional (3D) printers started to grow strongly in the field of drug delivery and personalized medicine, as they can tailor dosage forms according to the needs of each individual. This review gives an overview on the basic principles of layer-by-layer building of pharmaceutical dosage forms using different types of 3D printers. Also, the effect of infill percentage and pattern, raster orientation, layer thickness, thermal processing parameters on the printed formulations is highlighted. Additionally, the complex designs constructed by the 3D printers in order to modify the product shape, density, mucoadhesion and drug release are recapitulated. This review summarizes numerous applications for 3D printing in building drug-loaded structures including tablets, scaffolds, implants, microneedles, capsules, films, hydrogels, mouthguards, tubes, stents, vaginal suppositories and rings as well as in pediatric field. Finally, we suggest further investigational researches to aid in the widespread of 3D printing in the industrial pharmaceutical field. The 3D printing technology is expected to revolutionize drug delivery systems through customization of pharmaceutical formulations. [ABSTRACT FROM AUTHOR]

• Predictive models for FDM 3D printing were obtained using experimental design. • Drug quality parameters were interdependently affected by printing configurations. • The mechanical language of the printer was translated according to the prescription. • Integrating the responses allowed the printing setup to control the drug release. The present study aimed to analyze how the printing process affects the final state of a printed pharmaceutical product and to establish prediction models for post-printing characteristics according to basic printing settings. To do this, a database was constructed through analysis of products elaborated with a distinct printing framework. The polymers acrylonitrile butadiene styrene (ABS), polylactic acid (PLA), and high-impact polystyrene (HIPS) were tested in a statistically-based experiment to define the most critical printing factors for mass, mass variation, printing time, and porosity. Then, a predictive model equation was established and challenged to determine two different medical prescriptions. The factors of size scale, printlet format, and print temperature influenced printlet mass, while the printing time was impacted by size scale, printing speed, and layer height. Finally, increased printing speed leads to more porous printlets. The prescript-printed tablets showed average mass, mass variations, and porosity close to theoretical values for all filaments, which supports the adequacy of the optimized design of experiments for tablet production. Hence, printing settings can be preselected according to the desired product's characteristics, resulting in tablets produced with higher precision than usually achieved by compounding pharmacies. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) printing continuous carbon fiber-reinforced polylactic acid (PLA) composites offer excellent tensile mechanical properties. The present study aimed to research the effect of process parameters on the tensile mechanical properties of 3D printing composite specimens through a series of mechanical experiments. The main printing parameters, including layer height, extrusion width, printing temperature, and printing speed are changed to manufacture specimens based on the modified fused filament fabrication 3D printer, and the tensile mechanical properties of 3D printing continuous carbon fiber-reinforced PLA composites are presented. By comparing the outcomes of experiments, the results show that relative fiber content has a significant impact on mechanical properties and the ratio of carbon fibers in composites is influenced by layer height and extrusion width. The tensile mechanical properties of continuous carbon fiber-reinforced composites gradually decrease with an increase of layer height and extrusion width. In addition, printing temperature and speed also affect the fiber matrix interface, i.e., tensile mechanical properties increase as the printing temperature rises, while the tensile mechanical properties decrease when the printing speed increases. Furthermore, the strengthening mechanism on the tensile mechanical properties is that external loads subjected to the components can be transferred to the carbon fibers through the fiber-matrix interface. Additionally, SEM images suggest that the main weakness of continuous carbon fiber-reinforced 3D printing composites exists in the fiber-matrix interface, and the main failure is the pull-out of the fiber caused by the interface destruction. [ABSTRACT FROM AUTHOR]

In this article, the optimization of printing properties on a new, flexible ceramic substrate is reported for sensing and antenna applications encompassing internet of things (IoT) devices. E-Strate® is a commercially available, non-rigid, thin ceramic substrate for implementing in room temperature and high-temperature devices. In this substrate, the printing parameters like drop spacing, number of printed layers, sintering temperature, and sintering time were varied to ensure an electrically conductive and repeatable pattern. The test patterns were printed using silver nanoparticle ink and a Dimatix 2831 inkjet printer. Electrical conductivity, high-temperature tolerance, bending, and adhesion were investigated on the printed samples. The three-factor factorial design analysis showed that the number of printed layers, sintering temperature, sintering time, and their interactions were significant factors affecting electrical conductivity. The optimum printing parameters for the thin E-Strate® substrate were found to be 20 μm drop spacing, three layers of printing, and 300 °C sintering temperature for 30 min. The high-temperature tolerance test indicated a stable pattern without any electrical degradation. Repetitive bending, adhesion test, and ASTM tape tests showed adequate mechanical stability of the pattern. These results will provide insight for investigators interested in fabricating new IoT devices. [ABSTRACT FROM AUTHOR]

In this review, we discuss the parameters of fused deposition modeling (FDM) technology used in finished parts made from polyether ether ketone (PEEK) and also the possibility of printing small PEEK parts. The published articles reporting on 3D printed PEEK implants were obtained using PubMed and search engines such as Google Scholar including references cited therein. The results indicate that although many have been experiments conducted on PEEK 3D printing, the consensus on a suitable printing parameter combination has not been reached and optimized parameters for printing worth pursuing. The printing of reproducible tiny-sized PEEK parts with high accuracy has proved to be possible in our experiments. Understanding the relationships among material properties, design parameters, and the ultimate performance of finished objects will be the basis for further improvement of the quality of 3D printed medical devices based on PEEK and to expand the polymers applications. [ABSTRACT FROM AUTHOR]

Objective: To review the elements of the vat-polymerization workflow, including the 3D printing parameters, support structures, slicing, and post-processing procedures, as well as how these elements affect the characteristics of the manufactured dental devices., Data: Collection of published articles related to vat-polymerization technologies including manufacturing workflow description, and printing parameters definition and evaluation of its influence on the mechanical properties of vat-polymerized dental devices was performed., Sources: Three search engines were selected namely Medline/PubMed, EBSCO, and Cochrane. A manual search was also conducted., Study Selection: The selection of the optimal printing and supporting parameters, slicing, and post-processing procedures based on dental application is in continuous improvement. As well as their influence on the characteristics of the additively manufactured (AM) devices such as surface roughness, printing accuracy, and mechanical properties of the dental device., Results: The accuracy and properties of the AM dental devices are influenced by the technology, printer, and material selected. The printing parameters, printing structures, slicing methods, and the post-processing techniques significantly influence on the surface roughness, printing accuracy, and mechanical properties of the manufactured dental device; yet, the optimization of each one may vary depending on the clinical application of the additively manufactured device., Conclusions: The printing parameters, supporting structures, slicing, and post-processing procedures have been identified, but additional studies are needed to establish the optimal manufacturing protocol and enhance the properties of the AM polymer dental devices., Clinical Significance: The understanding of the factors involved in the additive manufacturing workflow leads to a printing success and better outcome of the additively manufactured dental device., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Four‐dimensional (4D) printing of shape memory materials has attracted increasing interests for personalized structures. In this study, a biocompatible poly(d,l‐lactide‐co‐trimethylene carbonate) (PLMC) is utilized to fabricate 4D shape‐changing structures with customized geometries through direct ink writing. The printed objects show shape transformations at different dimensions under thermal programming. The influence of the printing parameters on the properties including rheological, solvent evaporation, and static mechanical behavior are systematically investigated. A printing map is further depicted to achieve high‐quality printing with high viscous ink flowed from micronozzle to construct various structures. The printed structures in one‐dimensional, two‐dimensional, and three‐dimensional (3D) exhibit shape‐changing behavior with fast response around body temperature. The fast responsive time shows potential in the field of surgical suture (4 s), nonwoven fabric (3 s), and self‐expandable stent (35 s). The feasibility of 3D printing of PLMC opens the way for applications in shape‐changing devices with small diameter. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48177. [ABSTRACT FROM AUTHOR]

The current study reports the mechanical properties of 3D printing using multiple composite filaments, infill percentages, and printed structures. Results show that graphene‐contained polylactic acid (G‐PLA) displays the highest bending strength, of 119.50 MPa, improving by 62.7%, compared with pure PLA. The scanning electron microscopy (SEM) microstructural observations indicate that the high bending strength is caused by the pull‐out of graphene. As for the double‐filament layer‐by‐layer alternatively printed specimens, the obtained bending strengths are between the single‐filament specimens printed by the two filaments, respectively. Changing infill percentages from 30%, 65%, and to 100% prove that the mechanical properties are greatly enhanced. In the bending tests, with an increase in the infill percentage from 30% to 100%, it is found that all the bending strengths of G‐PLA, copper powder‐containing polylactic acid (Cu‐PLA), and carbon fibers‐containing Cf‐PLA increase by 63.7%, 130.1%, and 106.6% on account of enlarged cross‐section areas sustaining stress. Furthermore, in the compressive tests, shear stress is only found in the hexangular structure, which has a positive effect on the 32.1% increase of the compressive strength compared with that in the rectangular structure. It implies that printed structures significantly influence the fractured modes due to the variation of stress distribution in the designed structures. [ABSTRACT FROM AUTHOR]

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Additive manufacturing, or 3D printing, has become significantly more commonplace in tissue engineering over the past decade, as a variety of new printing materials have been developed. In extrusion-based printing, materials are used for applications that range from cell free printing to cell-laden bioinks that mimic natural tissues. Beyond single tissue applications, multi-material extrusion based printing has recently been developed to manufacture scaffolds that mimic tissue interfaces. Despite these advances, some material limitations prevent wider adoption of the extrusion-based 3D printers currently available. This progress report provides an overview of this commonly used printing strategy, as well as insight into how this technique can be improved. As such, it is hoped that the prospective report guides the inclusion of more rigorous material characterization prior to printing, thereby facilitating cross-platform utilization and reproducibility., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Regenerative medicine has been highlighted as one of the UK's 8 'Great Technologies' with the potential to revolutionize patient care in the 21st Century. Over the last decade, the concept of '3D bioprinting' has emerged, which allows the precise deposition of cell laden bioinks with the aim of engineering complex, functional tissues. For 3D printing to be used clinically, there is the need to produce advanced functional biomaterials, a new generation of bioinks with suitable cell culture and high shape/print fidelity, to match or exceed the physical, chemical and biological properties of human tissue. With the rapid increase in knowledge associated with biomaterials, cell-scaffold interactions and the ability to biofunctionalize/decorate bioinks with cell recognition sequences, it is important to keep in mind the 'printability' of these novel materials. In this illustrated review, we define and refine the concept of 'printability' and review seminal and contemporary studies to highlight the current 'state of play' in the field with a focus on bioink composition and concentration, manipulation of nozzle parameters and rheological properties., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)