3D printing in medicine for preoperative surgical planning: a review

The aim of this paper is to review the recent evolution of additive manufacturing (AM) within the medical field of preoperative surgical planning. The discussion begins with an overview of the different techniques, pointing out their advantages and disadvantages as well as an in-depth comparison of different characteristics of the printed parts. Then, the state-of-the-art with respect to preoperative surgical planning is presented. On the one hand, different surgical planning prototypes manufactured by several AM technologies are described. On the other hand, materials used for mimicking different living tissues are explored by focusing on the material properties: elastic modulus, hardness, etc. As a result, doctors can practice before performing surgery and thereby reduce the time needed for the operation. The subject of patient education is also introduced. A thorough review of the process that is required to obtain 3D printed surgical planning prototypes, which is based on different stages, is then carried out. Finally, the ethical issues associated with 3D printing in medicine are discussed, along with its future perspectives. Overall, this is important for improving the outcome of the surgery, since doctors will be able to visualize the affected organs and even to practice surgery before performing it.Postprint (author's final draft

3D Printing of Bioinert Oxide Ceramics for Medical Applications

Three-dimensionally printed metals and polymers have been widely used and studied in medical applications, yet ceramics also require attention. Ceramics are versatile materials thanks to their excellent properties including high mechanical properties and hardness, good thermal and chemical behavior, and appropriate, electrical, and magnetic properties, as well as good biocompati- bility. Manufacturing complex ceramic structures employing conventional methods, such as ceramic injection molding, die pressing or machining is extremely challenging. Thus, 3D printing breaks in as an appropriate solution for complex shapes. Amongst the different ceramics, bioinert ceramics appear to be promising because of their physical properties, which, for example, are similar to those of a replaced tissue, with minimal toxic response. In this way, this review focuses on the different medical applications that can be achieved by 3D printing of bioinert ceramics, as well as on the latest advances in the 3D printing of bioinert ceramics. Moreover, an in-depth comparison of the different AM technologies used in ceramics is presented to help choose the appropriate methods depending on the part geometry.Peer ReviewedPostprint (published version

Additive manufacturing of functional engineering components

Additive Manufacturing (AM) is a class of echnologies whereby components are made in an additive, layer-by-layer fashion enabling production of complex parts in which complexity has little or no effect on cost. However typical components roduced using these techniques are basic structural items with no major strength requirement and low geometric tolerances made from a single material. his thesis develops a low-cost Fused Filament abrication (FFF) based AM technique to produce functional parts. This is achieved by through esearching and implementing new materials in ombination and using precise control of infill tool paths for existing materials. Robocasting has previously been shown to be extremely versatile, however is known to offer poorer build quality relative to its ess-versatile counterparts. Research was ndertaken to enable Robocasting to be combined with FFF to enable the print quality and practical benefits of FFF with the material flexibility of Robocasting. This resulted in the manufacture of several multiple-material omponents using the technique to demonstrate its potential. In order to minimise the number of materials required to obtain desired properties, the effect of process parameters such as layer height, infill angle, and infill porosity were investigated. In total over an order of agnitude variation in Young’s modulus and tensile strength were achieved, enabling these properties to be actively controlled within the manufactured components. Finally a novel non-eutectic low melting point alloy was developed to be compatible with the FFF process. Its greater viscosity compared to traditional eutectics resulted in improved print quality and the reliable deposition of electrically conductive track 0.57x0.25mm in cross-section. In addition the material is approximately three orders of magnitude more conductive that typical printable organic inks. A micro-controller was produced using the technique in conjunction with traditional electronics components. This represents the first time a functional electrical circuitry, with sufficient conductivity for the majority of applications and interfacing directly with standard electrical components, has been produced using a very low-cost AM technique such as FFF. The research undertaken builds components with substantially improved functionality relative to traditional AM products, enabling electromechanical components with varying mechanical and electrical properties. It is anticipated that this could substantially reduce the part-count for many engineering assemblies and open up Additive Manufacturing to many new applications.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Suitability analysis for extrusion-based additive manufacturing process

Additive manufacturing (AM) is a widely applied manufacturing paradigm used for the layer-by-layer fabrication of desired components and objects, especially for those with highly intricate geometry. Extrusion-based AM, which is a subcategory of AM processing technologies, is characterized by the facilitation of controlled and successive deposition of feedstock AM materials through the nozzles of printer heads onto a print bed. Extrusion-based AM processing enables design freedom but offers cost efficiency and process simplicity when compared to other AM categories i.e. liquid- and powder-based AM technologies. The extrusion-based AM process has become increasingly widespread over the last two decades because of the expanding material options that can be used in this technology, and its capacity to be hybridised through the addition of multiple printheads or incorporation into a secondary manufacturing system. Despite the promising aspects of the extrusion-based AM process, increasing demands for customised extrusion-based printed products and an expanding range of extrusion-based AM materials create both material- and process-related challenges that limit the suitability of extrusion-based AM processes for some specific applications. Consequently, the principal objective of this review paper is to conduct a suitability analysis of extrusion-based AM processes. The suitability analysis follows a review and discussion about the extrusion-based AM process, and an assessment of easy- and hard-to-print extrusion-based AM materials. This paper, therefore, provides a comprehensive suitability analysis of each extrusion-based AM process while also providing some promising ideas for improving their current suitability levels. The findings and ratings reported in this paper importantly offers viewpoints that would support better futuristic comparisons between developed and developing extrusion-based AM processes, especially as businesses look to adopt the right AM solutions

Extrusion-based additive manufacturing technologies: State of the art and future perspectives

Extrusion-based additive manufacturing (AM) has recently become widespread for the layer-by-layer fabrication of three-dimensional prototypes and components even with highly complex shapes. This technology involves extrusion through a nozzle by means of a plunger-, filament- or screw-based mechanism; where necessary, this is preceded by heating of the feedstock material to reduce its viscosity sufficiently to facilitate extrusion. Extrusion-based AM offers greater design freedom, larger building volumes and more cost-efficient production than liquid- and powder-based AM processes. Although this technology was originally developed for polymeric filament materials, it is now increasingly applied to a wide variety of material classes, including metallic, edible and construction materials. This is in part thanks to the recent development of AM-specific feedstock materials (AM materials), in which materials that are not intrinsically suited to extrusion, for example because of high melting points or brittleness, are combined with other, usually polymeric materials that can be more readily extruded. This paper comprehensively and systematically reviews the state of the art in the field of extrusion-based AM, including the techniques applied and the individual challenges and developments in each materials class for which the technology is being developed. The paper includes material- and process-centred suitability analysis of extrusion-based AM, and a comparison of this technology with liquid- and powder-based AM processes. Prospective applications of this technology are also briefly discussed

Additive manufacturing of bioactive glass biomaterials

Tissue engineering (TE) and regenerative medicine have held great promises for the repair and regeneration of damaged tissues and organs. Additive manufacturing has recently appeared as a versatile technology in TE strategies that enables the production of objects through layered printing. By applying 3D printing and bioprinting, it is now possible to make tissue-engineered constructs according to desired thickness, shape, and size that resemble the native structure of lost tissues. Up to now, several organic and inorganic materials were used as raw materials for 3D printing; bioactive glasses (BGs) are among the most hopeful substances regarding their excellent properties (e.g., bioactivity and biocompatibility). In addition, the reported studies have confirmed that BG-reinforced constructs can improve osteogenic, angiogenic, and antibacterial activities. This review aims to provide an up-to-date report on the development of BG-containing raw biomaterials that are currently being employed for the fabrication of 3D printed scaffolds used in tissue regeneration applications with a focus on their advantages and remaining challenges

Polymer-zirconia based ceramic composites produced by 3D-printing

(English) Zirconia ceramic is widely used in numerous fields, such as electronics, machinery, and biomedical applications, due to its excellent properties as chemical resistance, thermal stability, electrical resistance, toughness, hardness, but also inertness and g biocompatibility. The 3D-printing technology has opened new doors for possible applications of zirconia and also allows for higher complexity of the shapes and structures, even for specimens with designed porosity, which would be until now unimaginable with traditional manufacturing methods like gel casting or cold isostatic pressing. The biocompatibility, inertness, and excellent aesthetic aspects of this ceramic make it also a preferred material for biomedical applications, more specifically in dentistry. However, application in the biomedical field has had some shortcomings, where the high hardness and brittleness of the material could cause discomfort or excessive wear. One of the aims of this thesis was to develop a new hybrid material that would complement the above-mentioned properties of zirconia and at the same time try to mimic the mechanical properties and biocompatibility of natural teeth using a combination of zirconia and acrylate polymer materials, while using additive manufacturing. The first part was focused on the development and manufacturing of such material. The idea of polymer-infiltrated ceramic networks (PICN), where a porous sintered ceramic structure is interpenetrated with a polymer matrix, was followed. The innovation of this technology was based on the 3D-printing of ceramic zirconia (3Y-TZP) scaffolds with designed porosity. After the optimization of the printing process, the 50% zirconia infill was chosen as the most appropriate porosity of the scaffold that was subsequently infiltrated with bisphenol A glycerolate dimethacrylate (Bis-GMA) and triethylene glycol dimethacrylate (TEGDMA) copolymer. After the successful manufacturing of 3D-printed PICN and the proper infiltration of the copolymer, the physical-chemistry properties of the new material were characterized, as well as its mechanical properties. The bacterial adhesion was evaluated against Gram-negative Escherichia coli and Gram-positive Streptococcus salivarius bacteria lines, revealing, that although such samples do not have antimicrobial properties, they do not promote excessive bacterial growth either. Regarding biocompatibility, the cell assay using human osteoblasts (MG-63) was carried out showing good cell viability. To improve the antimicrobial properties of manufactured PICN, the surface was modified with the adhesion of silver nanoparticles, which were embedded in an enzymatically modified phenolated lignin matrix (Ag@PL NPs), obtained from renewable resources, to avoid metal particle oxidation. The functionalization of the surface of the hybrid material with such Ag NPs allowed the reduction of bacterial growth by 90% on the modified surface. The last part of this thesis focused on the improvement of osseointegration of zirconia surface in vitro. Although it is an inert material, surface modification is required to avoid possible failures of zirconia once implanted in vivo. A polydopamine methacrylate copolymer, which has proved antibiofilm formation properties, was applied to the surface of zirconia. Characterization of the surfaces has proven good viability of the MG-63 cell line and also a great adhesion of the polymeric nanofilm, produced by cold plasma to the surface of zirconia discs. Overall, this thesis describes the 3D printing of PICN structures, which have a macroporous structure for the correct infiltration of the copolymer. The synergy and good adhesion between these materials have given rise to a prototype whose mechanical properties simulate those for natural teeth(Español)La zirconia es un material ampliamente utilizado en electrónica y en la biomedicina debido a su estabilidad química, estabilidad térmica, resistencia eléctrica, dureza, alta tenacidad, y biocompatibilidad debido a su naturaleza inerte. Con el desarrollo de la tecnología de fabricación aditiva (o 3D-printing), se han propuesto nuevas aplicaciones para la zirconia hasta ahora inimagibles empleando métodos de producción convencionales. Con la fabricación 3D se consiguen estructuras más complejas, con geometrías más variables y con un mayor control de la de porosidad. Estas características convierten esta cerámica en uno de los materiales predilectos para aplicaciones biomédicas, especialmente en la odontología. No obstante, la dureza y fragilidad del material son dos limitaciones para su aplicación en la producción de biomateriales, debido a que pueden llevar al desgate de las estructuras y generar discomfort en el paciente. Uno de los objetivos de esta tesis fue el desarrollo por fabricación aditiva de nuevos materiales híbridos a base de zirconia y polímeros acrilatos para simular las propiedades mecánicas y la buena biocompatiblidad características de los dientes naturales. La primera parte estuvo enfocada en el desarrollo de dichos materiales, con la elaboración de redes cerámicas infiltradas por polímeros (PICN), en las cuales una estructura cerámica porosa sinterizada es interprenetada por una matriz de polímero. La innovación fue el diseæo de andamios de zirconia (3Y-TZP), impresas tridimensionalmente y con porosidad controlada y ajustada. Después de la optimización de impresión, se decidió trabajar con un porcentaje de relleno del 50 % de zirconia para obtener la porosidad adecuada de la matriz, que fue después infiltrada con dimetacrilato de glicerolato de bisfenol A y trietilenglicol dimetacrilato (Bis-GMA y TEGDMA).Tras la producción de las estructuras PICN y la infiltración del copolímero, los materiales generados fueron completamente caracterizados por técnicas físico-químicas y las propiedades mecánicas fueron analizadas. Ensayos de adhesión bacteriana fueron llevados a cabo con las bacterias Escherichia coli (Gram-negativa) y Stretoccocus salivarius (Gram-positiva) concluiendo que, a pesar de la ausencia de efecto antibacteriano del material híbrido, tampoco existe una promoción del crecimiento bacteriano en dicha superficie. Respecto a la biocompatibilidad, experimentos con la línea celular MG-63 mostraron altos porcentajes de viabilidad celular. Para mejorar las propiedades antimicrobianas de las PICN, la superficie fue modificada con nanopartículas de plata, las cuales fueron embebidas en una matriz de lignina modificada enziméticamente con fenolatos (Ag@PL NPs) para evitar su oxidación. La funcionalización de la superficie del material híbrido con dichas nanopartículas permitió reducir el crecimiento bacteriano en un 90 %, respecto a la superficie no modificada. La última parte de la tesis estuvo enfocada en realizar mejoras en la oseointegración de la zirconia in vitro. Apesar de que es un material inerte, funcionalización de su superficie es recommendable para evitar futuros rechazos de la zirconia una vez implantada in vivo. Un copolímero de metacrilato de polidopamina, el cual previene la formación de biopelículas bacterianas, fue escogido para recubrir la superficie de zirconia. La caracterización demostró una gran adhesión del nuevo polímero, generado por plasma frío, a la superficie plana de discos de zirconia, además de una buena viabilidad de las células de la línea MG-63, en principio atribuída a la presencia de la polidopamina. En conclusión, esta tesis describe el proceso de impresión 3D de estructuras PICN, las cuales tienen una estructura macroporosa para la correcta infiltración del copolímero. La sinergia y la buena adherencia entre estos distintos materiales ha dado origen a un prototipo cuyas propiedades mecánicas simulan aquellas descritas para los dientes naturales. Además, las modificaciones de la superficie de la zirconia (plana o en format 3D filamentoso) con el fin de mejorar las propiedades del composite, ha resultado sactisfactoria para profundizar dicha investigación en el campo odontológico, permitiendo nuevas vías para ampliar el espectro de aplicaciones de dichos materiales híbridos en otros campos biomédicos.Polímers i biopolímer

Materials and process design for ceramic fused filament fabrication (CF3) of hydroxyapatite.

Ceramic fused filament fabrication (CF3) enables the fabrication of highly customizable ceramic parts at relatively lower costs compared to other AM technologies. Advanced ceramics, having specific or niche applications, call for a high level of accuracy to meet the performance requirements. For achieving the desired level of accuracy in any manufacturing process, it is important to know the effect of involved parameters at different stages of fabrication. CF3 has been around for a while but there has been a severe lack of literature dealing with understanding the effect of process parameters on the final part properties. In this study, Hydroxyapatite (HAp) components with 75 wt.% solids loading filaments were prepared. A DOE was conducted to analyze and establish the relationship between process parameters and the final printed part properties. Extrusion multiplier, % infill, and print speed were taken as input parameters and the effect of their effect on final part dimensions, layer thickness, bead width, and surface roughness were analyzed. Additionally, the experimental data was analyzed using regression analysis, analysis of variance (ANOVA), % contribution, and main effects using Minitab software. ` vi Furthermore, to establish the capability of HAp CF3 in biomedical applications, HAp and its composite parts with 10 wt.% Si3N4 (HAp10SN) were fabricated. Homogeneous feedstock with 63 wt.% ceramic powder was prepared and used to extrude filaments for further printing using a desktop printer. Our results showed that the addition of Si3N4 to HAp increases the feedstock viscosity. However, the filaments and CF3 parts made using HAp and HAp10SN feedstocks exhibited comparable densities without gross defects. We have obtained relatively smoother CF3 parts with HAp10SN than pure HAp, which is attributed to their high feedstock viscosity and formation of the liquid phase during sintering. Sintering at 1250 °C for 4 h in air, after thermal debinding, resulted in a relative density of ~85% with HAp and tricalcium phosphate (TCP) as major constituents. Sintered HAp10SN samples also revealed an almost 70% reduction in the grain size and 147% increase in the hardness compared to pure HAp. Our results indicate that the CF3 processed HAp10SN samples containing ~15% porosity, Si3N4 particles, and Si-substituted HAp/TCP have strong potential as bone replacements

Experimental Analysis of Plastic-Based Composites Made by Composite Plastic Manufacturing

The significance of composites cannot be overstated in the manufacturing sector due to their unique properties and high strength-to-weight ratio. The use of thermoplastics for composites manufacturing is also gaining attention due to their availability, ease of operation, and affordability. However, the current methods for plastic-based composites are limited due to the requirements of long curing times and pre- and post-treatment, thereby resulting in longer lead times for the desired product. These methods also limit the freedom to operate with different forms of materials. Therefore, a new manufacturing process for plastic-based composites is required to overcome such limitations. This research presents a new manufacturing process to produce high-quality plastic-based composites with bespoke properties for engineering applications. The process is referred to as Composite Plastic Manufacturing (CPM) and is based on the principle of fused filament fabrication (FFF) equipped with a heat chamber. The process integrates two material extrusion additive manufacturing technologies, i.e., filament and syringe extrusion. The paper presents the principle of the process, both in theory and in practice, along with the methodology and materials used to manufacture plastic composites. Various composites have been manufactured using the CPM process with thermally activated materials and tested according to British and International standards. Polylactic Acid (PLA) has been interlaced with different thermally activated materials such as graphene-carbon hybrid paste, heat cure epoxy paste, and graphene epoxy paste. The process is validated through a comparative experimental analysis involving tests such as ultrasonic, tensile, microstructural, and hardness to demonstrate its capabilities. The results have been compared with commercially available materials (PLA and Graphene-enhanced PLA) as well as literature to establish the superiority of the CPM process. The CPM composites showed an increase of up to 10.4% in their tensile strength (54 MPa) and 8% in their hardness values (81 HD) when compared to commercially available PLA material. The composites manufactured by CPM have also shown strong bonding between the layers of PLA and thermally activated materials; thus, highlighting the effectiveness of the process. Furthermore, the composites showed a significant increase of up to 29.8% in their tensile strength and 24.6% in their hardness values when compared to commercially available Graphene-enhanced PLA material. The results show that the CPM process is capable of manufacturing superior quality plastic composites and can be used to produce products with bespoke properties

A Guide to Additive Manufacturing

This open access book gives both a theoretical and practical overview of several important aspects of additive manufacturing (AM). It is written in an educative style to enable the reader to understand and apply the material. It begins with an introduction to AM technologies and the general workflow, as well as an overview of the current standards within AM. In the following chapter, a more in-depth description is given of design optimization and simulation for AM in polymers and metals, including practical guidelines for topology optimization and the use of lattice structures. Special attention is also given to the economics of AM and when the technology offers a benefit compared to conventional manufacturing processes. This is followed by a chapter with practical insights into how AM materials and processing parameters are developed for both material extrusion and powder bed fusion. The final chapter describes functionally graded AM in various materials and technologies. Throughout the book, a large number of industrial applications are described to exemplify the benefits of AM