45S5 Bioactive Glass: Comprehensive Swot Analysis and Future Prospects in Tissue Engineering

Purpose The development of additive manufacturing (AM) techniques has significantly expanded the design space for engineering structures and facilitated the practical application of novel concepts, such as meta-materials with diverse microstructures. However, in load-bearing applications—particularly in aerospace and aeroengine fields—additively manufactured (AMed) metallic materials and structures still face limitations due to the presence of inherent defects. For meta-materials, the geometric accuracy of microstructural cells is also difficult to ensure using current metal AM technologies. These defects and geometric inaccuracies can markedly affect the mechanical properties of mechanical meta-materials. Consequently, a substantial body of research has focused on investigating the mechanical behavior and performance of AMed mechanical meta-materials. This paper presents a comprehensive review of recent advancements in metal AM technologies, with a particular focus on defect characterization methods and the evaluation of strength and fatigue properties in AMed mechanical meta-materials. Design/methodology/approach This paper provides a state-of-the-art review on the AM techniques for mechanical meta-materials, defects and defect characterization methods in AMed structures, and evaluation methods of strength and fatigue properties of mechanical meta-materials. Findings Metal AM techniques for mechanical meta-materials, like selective laser melting, wire-arc AM, etc, and recently developed technologies like, online inspection during the AM process, are reviewed. The defects in AMed meta-materials, along with the corresponding characterization methods, are systematically summarized. Additionally, this paper presents a comprehensive overview of evaluation approaches for the strength and fatigue properties of mechanical meta-materials, encompassing experimental testing, theoretical modeling, numerical simulation, and machine learning techniques. Future perspectives on manufacturing and the mechanical property study of mechanical meta-materials are also given. Originality/value A systematic summary of metal AM techniques, as well as defect detection and characterization methods in AMed mechanical meta-materials, is provided. Furthermore, the paper presents a comprehensive review of the mechanical properties of mechanical meta-materials, with a particular focus on strength and fatigue performance.

Auxetic structures are a special class of structural components that exhibit a negative Poisson’s ratio (NPR) because of their constituent materials, internal microstructure, or structural geometry. To realize such structures, specialized manufacturing processes are required to achieve a dimensional accuracy, reduction of material wastage, and a quicker fabrication. Hence, additive manufacturing (AM) techniques play a pivotal role in this context. AM is a layer-wise manufacturing process and builds the structure as per the designed geometry with appreciable precision and accuracy. Hence, it is extremely beneficial to fabricate auxetic structures using AM, which is otherwise a tedious and expensive task. In this study, a detailed discussion of the various AM techniques used in the fabrication of auxetic structures is presented. The advancements and advantages put forward by the AM domain have offered a plethora of opportunities for the fabrication and development of unconventional structures. Therefore, the authors have attempted to provide a meaningful encapsulation and a detailed discussion of the most recent of such advancements pertaining to auxetic structures. The article opens with a brief history of the growth of auxetic materials and later auxetic structures. Subsequently, discussions centering on the different AM techniques employed for the realization of auxetic structures are conducted. The basic principle, advantages, and disadvantages of these processes are discussed to provide an in-depth understanding of the current level of research. Furthermore, the performance of some of the prominent auxetic structures realized through these methods is discussed to compare their benefits and shortcomings. In addition, the influences of geometric and process parameters on such structures are evaluated through a comprehensive review to assess their feasibility for the later-mentioned applications. Finally, valuable insights into the applications, limitations, and prospects of AM for auxetic structures are provided to enable the readers to gauge the vitality of such manufacturing as a production method.

Two types of additive manufacturing (AM) techniques, fused filament fabrication (FFF) and selective laser sintering (SLS), were employed to fabricate specimens from three widely used AM polymers: polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), and polyamide (PA): the first two using FFF and PA using SLS. The single‐edge notch bending (SENB) test was employed to measure the mode‐I fracture toughnesses of bulk and AM specimens in three directions relative to the printing direction. Unlike their bulk counterparts, AM polymers exhibited anisotropic fracture toughness. The degree of anisotropy in FFF‐PLA was much larger than FFF‐ABS and SLS‐PA. The smallest fracture toughness value for each AM polymer was achieved along the transverse printing direction. Different AM techniques affect fracture toughness differently. For instance, FFF is shown to increase PLA's plastic deformation, while SLS reduces PA's ductility. The decrease in fracture toughness is consistently observed when transitioning from bulk polymers to AM ones, reaching as much as 75%. This study provides insights into the fracture toughness of AM parts made via popular plastics, which are crucial for designing structural parts using FFF and SLS processes.

Chapter 7 - Additive manufacturing techniques used for preparation of scaffolds in bone repair and regeneration

Metallic biomedical implants are made from materials such as stainless steel, titanium, magnesium, and cobalt-based alloys. As a degradable biometal, magnesium (Mg) and its alloys are becoming more popular for applications in bone tissue engineering. Mg-based alloys have been found to be biocompatible, bioabsorbable, and bioactive, allowing them to be used as orthopedic implants with a low Young’s modulus. Computer-aided design can be used to design scaffolds with intricate porous structures based on patient-specific anatomical data. These models can be materialized rapidly and with reasonably acceptable dimensional accuracy by additive manufacturing (AM) techniques. It is known that lasers are the most widely investigated energy source for AM’ed Mg, as they offer some distinct advantages over other forms of energy. Recent studies have focused on developing biodegradable Mg scaffolds by using laser-based AM techniques. In this paper, we aim to review the recent progress of laser-based AM for Mg alloys and survey challenges in the research and future development of AM’ed Mg scaffolds for clinical applications.

While the design of complex shaped parts is enabled using additive manufacturing (AM) techniques, the need for tailoring microstructures catering to the requirements of specific applications must not be neglected. Considering the level of design complexity involved in the design of parts for ballistic applications, AM techniques may be envisaged to be employed in their design. On the other hand, there are innumerous reports, especially since the last decade, on a new class of metallic materials known as high-entropy alloys (HEAs) or multicomponent alloys, extensively investigated for their microstructure-property relation for a number of different applications. However, it may be noted that such studies are mainly limited to fundamental research and have not systematically focussed on correlating the findings of fundamental research with real-time applications. Therefore, considering that both AM and HEAs are relatively "new" and "booming" areas of research, the present book chapter provides a review on the development of AM HEAs towards designing components (e.g. armors) with high resistance to dynamic impact applications, in order to qualify themselves as alternatives and even superior to conventional materials (such as steels) for high-end ballistic applications. Additionally, this chapter will also focus on the challenges associated with employing AM HEAs for these applications and provide a roadmap for both fundamental and industrial research through strategies to design AM HEAs.

Additive manufacturing (AM), or 3D printing, has attracted substantial attention in the aerospace sector due to its potential for complex part manufacturing, reduced material waste, and greater design freedom. The integration of robot-assisted systems with additive manufacturing (AM) techniques has demonstrated the potential to enhance efficiency, precision, and scalability. This review paper seeks to investigate recent advancements in robot-assisted AM for aerospace applications, emphasizing their impact on the industry and discussing future possibilities. The concept of robot-assisted additive manufacturing has been addressed and its advantages over traditional methods are highlighted. A complete examination of contemporary research and breakthroughs in this sector is offered, covering wire arcing additive manufacturing, laser metal deposition, and the extrusion of composite materials. The hardware implementation, printing material utilization, and printing path planning methods are investigated for the AM of metallic and fiber-reinforced composite materials. The challenges connected with robot-assisted AM, including system calibration, accuracy, and adaptability to complicated geometries, have been studied as well. Overall, the insights presented will be beneficial for researchers, engineers, and industry professionals working in aerospace manufacturing, paving the path for the next generation of robot-assisted AM techniques.

The technique used to produce a 3D tissue engineering (TE) scaffold is of fundamental importance in order to guarantee its proper morphological characteristics. An accurate assessment of the resulting structural properties is therefore crucial in order to evaluate the effectiveness of the produced scaffold. Synchrotron radiation (SR) computed microtomography (μ-CT) combined with further image analysis seems to be one of the most effective techniques to this aim. However, a quantitative assessment of the morphological parameters directly from the reconstructed images is a non trivial task. This study considers two different poly(ε-caprolactone) (PCL) scaffolds fabricated with a conventional technique (Solvent Casting Particulate Leaching, SCPL) and an additive manufacturing (AM) technique (BioCell Printing), respectively. With the first technique it is possible to produce scaffolds with random, non-regular, rounded pore geometry. The AM technique instead is able to produce scaffolds with square-shaped interconnected pores of regular dimension. Therefore, the final morphology of the AM scaffolds can be predicted and the resulting model can be used for the validation of the applied imaging and image analysis protocols. It is here reported a SR μ-CT image analysis approach that is able to effectively and accurately reveal the differences in the pore- and throat-size distributions as well as connectivity of both AM and SCPL scaffolds.

Additively manufactured materials and structures: A state-of-the-art review on their mechanical characteristics and energy absorption

4 - Biofabrication via integrated additive manufacturing and electrofluidodynamics

This paper describes the synthesis and evaluation of samarium-doped 45S5 bioactive glass in various ratios. The bioactive glass samples were prepared using the sol–gel method and subjected to a heat treatment at 700 °C in normal atmosphere. The obtained samples were analyzed by thermogravimetric analysis (TGA) before and after the heat treatment to assess their thermal stability and compositional changes. The bioactivity of the samples was tested in vitro by immersion in simulated body fluid (SBF) at 36.5 ± 0.5 °C (normal human body temperature) and pH 7.4 (the pH of the human blood plasma), for several time periods. During the test, the pH and conductivity of the SBF solutions were monitored to track ion migration. After the in vitro test, the mass loss was evaluated and the formation of hydroxycarbonate apatite (HCA) was analyzed by FTIR spectroscopy. The microstructure of the bioactive glasses was examined using scanning electron microscopy (SEM) and the density of bioactive glass was also determined using Archimedes’ principle. This study also investigated the antimicrobial and anti-biofilm properties of both undoped and samarium-doped 45S5 bioactive glass through qualitative and quantitative assays against a range of microorganisms, including Gram-negative, Gram-positive, and yeast reference strains. The results were compared with literature data on melt-derived bioactive glass to evaluate the effects of Sm doping and the sol–gel synthesis method on bioactive glass performance.

The performance of quadcopter frames, particularly in terms of weight and crash resistance, is significantly influenced by their structural design and manufacturing process. In this work, a methodology is proposed that integrates advanced principles of topology optimization (TO) and additive manufacturing (AM) techniques to optimize the frame structure for improved performance. First, an analysis is conducted to evaluate existing quadcopter frame configurations, identifying areas for improvement. Experimental evaluations of thrust and moment of motors are performed to assess the performance of the enhanced quadcopter frame, with a focus on advancing the design through computer-aided simulations of static structural analysis and impact tests. The TO technique is then employed to determine the optimal distribution of material within the frame, governed by constraints such as weight reduction and mechanical strength. The results demonstrate that the overall performance of a quadcopter frame is significantly improved by the proposed methodology, showcasing advancements in stability, weight reduction, and crashworthiness. The resulting optimized frame design is subsequently manufactured using AM methods, which offer advantages such as design flexibility and the ability to produce complex geometries. The findings of this study contribute to the field of quadcopter design and optimization by highlighting the synergies between TO and AM techniques. An avenue is offered for the development of lightweight and robust quadcopter frames, as the capabilities and performance of quadcopter systems are advanced. The insights gained from this research open up opportunities for further advancements in the design and manufacturing of UAVs.

Thermal and mechanical characterization of OMMT nano clay treated ABS parts via acetone deposition technique

Nanoporous materials are categorized as microporous (pore sizes 0.2-2nm), mesoporous (pore sizes 2-50nm), and macroporous (pore sizes 50-1000nm). Mesoporous silica (MS) has gained a significant interest due to its notable characteristics, including organized pore networks, specific surface areas, and the ability to be integrated in a variety of morphologies. Recently, MS has been widely accepted by range of manufacturer and as drug carrier. Moreover, silica nanoparticles containing mesopores, also known as mesoporous silica nanoparticles (MSNs), have attracted widespread attention in additive manufacturing (AM). AM commonly known as three-dimensional printing is the formalized rapid prototyping (RP) technology. AM techniques, in comparison to conventional methods, aid in reducing the necessity for tooling and allow versatility in product and design customization. There are generally several types of AM processes reported including VAT polymerization (VP), powder bed fusion (PBF), sheet lamination (SL), material extrusion (ME), binder jetting (BJ), direct energy deposition (DED), and material jetting (MJ). Furthermore, AM techniques are utilized in fabrication of various classified fields such as architectural modeling, fuel cell manufacturing, lightweight machines, medical, and fabrication of drug delivery systems. The review concisely elaborates on applications of mesoporous silica as versatile material in fabrication of various AM-based pharmaceutical products with an elaboration on various AM techniques to reduce the knowledge gap.

This thesis reports investigations on Additive Manufacturing (AM) techniques, namely valvejet technology and fused deposition modelling for the production of personalised dosage forms of low dose and low-melting drugs. Inkjet printing has been examined by several research groups for its potential to dispense pharmacological agents into final products, ranging from solid oral dosage forms to functionalized medical devices. However, the thermal and piezoelectric print heads reported in these investigations are best suited to printing solution and nano-suspension inks with particle sizes, solvents and rheological parameters in a narrow range specified by their manufacturers. In the work presented here, we examined a more robust valvejet (â electromagneticâ ) technology which allows coarse and viscous micro-suspensions to be dispensed with high accuracy and precision. More than 40% of newly discovered drugs and an estimated 90% of pipeline drugs are poorly soluble, so there is a clear need for robust printing methods, suitable for printing coarse suspensions. Paracetamol and indomethacin were selected to demonstrate the feasibility of printing soluble and poorly soluble APIs in the form of solution and suspension inks respectively. Valvejet technology has been investigated as a means of depositing solutions with a broader range of viscosity and suspensions with average particle sizes exceeding 2 μm. Printed samples were characterised for their morphology, chemical and solid-sate properties of the active ingredient and content uniformity and mechanical robustness of the coatings. Results from this investigation were used to develop a fixed dose combination of pharmacologically relevant fixed dose combination of ramipril and glimepiride. Also, valvejet technology (being devoid of temperature and stress elements often associated with most additive manufacturing techniques) has been demonstrated to be a promising alternative for producing personalised drug products of drugs that are susceptible to processing conditions. Fused deposition modeling (FDM) is the most commonly investigated of the additive manufacturing techniques to produce drug products and is well suited for the production of high-dose dosage forms. Higher temperatures associated with FDM is the major limiting factor in application of this technique for lower-melting drugs. Kollidon VA64 and Kollidon 12PF, immediate release polymers and PEG 1500 as the primary plasticizer have been investigated to lower the FDM temperature to <100 °C. Ramipril a thermolabile drug with a low melting point 109 °C has been chosen as model drug, the filaments of which were produced using Kollidon VA64 and Kollidon 12PF and was printed at 90 °C- the lowest temperature reported until this work was published and is the lowest melting point drug investigated to date by FDM printing. Developing a library of polymer and excipient combinations that are suited for FDM printing at lower temperatures deserves further investigation.