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The purpose of this paper is to demonstrate an innovative, fast and low-cost method to fabricate customized stents using polyurethane-based shape memory polymers composite reinforced by cellulose nanocrystal (CNC), achieved by a commercial desktop extrusion-based additive manufacturing (EBAM) device.

The composite filament for printing the stents was prepared by a two-step melt-compounding extrusion process. Afterward, the stents were produced by a desktop EBAM printer. Thermal characterizations, including thermo-gravimetric analysis (TGA) and modulated differential scanning calorimetry (modulated DSC), were conducted on stent samples and filament samples, respectively. Then the stents were programmed under 45°C. Recovery characterizations, including recovery force and recovery ratio measurement, were conducted under 40°C.

TGA results showed that the materials were stable under the printing temperature. Modulated DSC results indicated that, with the addition of CNCs, the glass transition temperature of the material dropped slightly from 39.7°C at 0 Wt.% CNC to 34.2°C at 7 Wt.% CNC. The recovery characterization showed that the stents can exert a maximum recovery force of 0.4 N/mm when 7 Wt.% of CNCs were added and the maximum recovery ratio of 35.8% ± 5.1% was found when 4 Wt.% of CNCs were added. The addition of CNC improved both the recovery ratio and the recovery force of the as-prepared stents.

In terms of recovery force, the as-prepared stents out-performed commercially available stents by 30 times. In addition, additive manufacturing offers more flexibility in the design and fabrication of customized cardiovascular stents.

The purpose of this paper is to demonstrate the feasibility of using shape memory polymer (SMP) for developing vascular stent. In particular, the expansion performance is analyzed through extensive modeling and simulation.

Firstly, the authors construct the model geometry and propose a constitutive model to describe the deformation of the stent due to the expansion process. The authors then simulate the expansion process under varying conditions, including different heating rates and recovery temperatures. Finally, the authors analyze the radial strength of the SMP stent.

A less invasive and stable expansion performance of the SMP stent is confirmed by the simulation method. A fitting function of the expansion process is proposed based on the characteristics of the SMP.

The effects of dynamic blood flow on the SMP stent is ignored. A fluid-structure interaction analysis may need to be considered to give a more accurate description of the behaviour of the SMP stent.

The findings will provide guidance for the rational design and application of SMP stents.

The work will provide guidance for the new generation stent design.

This is the first time that the expansion performance of a SMP stent has been analyzed both qualitatively and quantitatively through modelling and simulation.

The development of new advanced materials, such as photopolymerizable resins for use in stereolithography (SLA) and Ti6Al4V manufacture via selective laser melting (SLM) processes, have gained significant attention in recent years. Their accuracy, multi-material capability and application in novel fields, such as implantology, biomedical, aviation and energy industries, underscore the growing importance of these materials. The purpose of this study is oriented toward the application of new advanced materials in stent manufacturing realized by 3D printing technologies.

The methodology for designing personalized medical devices, implies computed tomography (CT) or magnetic resonance (MR) techniques. By realizing segmentation, reverse engineering and deriving a 3D model of a blood vessel, a subsequent stent design is achieved. The tessellation process and 3D printing methods can then be used to produce these parts. In this context, the SLA technology, in close correlation with the new types of developed resins, has brought significant evolution, as demonstrated through the analyses that are realized in the research presented in this study. This study undertakes a comprehensive approach, establishing experimentally the characteristics of two new types of photopolymerizable resins (both undoped and doped with micro-ceramic powders), remarking their great accuracy for 3D modeling in die-casting techniques, especially in the production process of customized stents.

A series of analyses were conducted, including scanning electron microscopy, energy-dispersive X-ray spectroscopy, mapping and roughness tests. Additionally, the structural integrity and molecular bonding of these resins were assessed by Fourier-transform infrared spectroscopy–attenuated total reflectance analysis. The research also explored the possibilities of using metallic alloys for producing the stents, comparing the direct manufacturing methods of stents’ struts by SLM technology using Ti6Al4V with stent models made from photopolymerizable resins using SLA. Furthermore, computer-aided engineering (CAE) simulations for two different stent struts were carried out, providing insights into the potential of using these materials and methods for realizing the production of stents.

This study covers advancements in materials and additive manufacturing methods but also approaches the use of CAE analysis, introducing in this way novel elements to the domain of customized stent manufacturing. The emerging applications of these resins, along with metallic alloys and 3D printing technologies, have brought significant contributions to the biomedical domain, as emphasized in this study. This study concludes by highlighting the current challenges and future research directions in the use of photopolymerizable resins and biocompatible metallic alloys, while also emphasizing the integration of artificial intelligence in the design process of customized stents by taking into consideration the 3D printing technologies that are used for producing these stents.

The purpose of this paper is to fabricate pre-existing geometries of the stents using solvent cast 3D printing (SC3P) and encapsulation of each stent with heparin drug by using aminolysis reaction.

The iron pentacarbonyl powder and poly-ɛ-caprolactone blend (PCIP) were used to print stent designs of Art18z, Palmaz-Schatz and Abbott Bvs1.1. The properties of antithrombosis, anticoagulation and blood compatibility were introduced in the stents by conjugation of heparin drug via the aminolysis process. The aminolysis process was confirmed by energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy due to presence of amide group and nitrogen peak in the respective analysis. Biological studies were performed to depict the cell viability, hemocompatibility and antithrombotic properties. Besides, mechanical behaviors were analyzed to study the behavior of the stents under radial compression load and bending load.

The amount of heparin immobilized on the Art18z, Palmaz-Schatz and Abbott Bvs1.1 stents were 255 ± 27, 222 ± 30 and 212 ± 13 µg, respectively. The cell viability studies using L929 fibroblast cells confirmed the cytocompatibility of the stents. The heparinized SC3P printed stents displayed excellent thrombo-resistance, anticoagulation properties and hemocompatibility as confirmed by blood coagulation analysis, platelet adhesion test and hemolysis analysis. Besides, mechanical behavior was found in context of the real-life stents. All these assessments confirmed that the developed stents have the potential to be used in the real environment of coronary arteries.

Various customized shaped biodegradable stents were fabricated using 3D printing technique and encapsulated with heparin drug using aminolysis process.

Stent malapposition is one of the most significant precursors of stent thrombosis and restenosis. Adverse haemodynamics may play a key role in establishing these diseases, although numerical studies have used idealised drug transport models to show that drug transport from malapposed drug-eluting stent struts can be significant. This paper aims to study whether drug transport from malapposed struts is truly significant. Another aim is to see whether a streamlined strut profile geometry – with a 61% smaller coating but a 32% greater coating-tissue contact area – can mitigate the adverse haemodynamics associated with stent malapposition while enhancing drug uptake.

Two- and three-dimensional computational fluid dynamics simulations were used in this study. Unlike past simulations of malapposed drug-eluting stent struts, a qualitatively validated drug-transport model which simulates the non-uniform depletion of drug within the drug coating was implemented.

It was shown that even a 10-µm gap between the strut and tissue dramatically reduces drug uptake after 24 h of simulated drug transport. Furthermore, the streamlined strut profile was shown to minimise the adverse haemodynamics of malapposed and well-apposed stent struts alike and enhance drug uptake.

Unlike prior numerical studies of malapposed stent struts, which did not model the depletion of drug in the drug coating, it was found that stent malapposition yields negligible drug uptake. The proposed semicircular-profiled strut was also shown to be advantageous from a haemodynamic and drug transport perspective.

In this paper a numerical simulation analysis of a modified stent-based electrode is introduced to be used as a bipolar electrode for radio frequency ablation of tumours located in hollow organs. The purpose of this paper is to study the possibility of achieving a more regular volume of induced lesion with the presented electrode without imperilling the ductal organ where the tumour is located.

Three types of bipolar electrode configurations were considered, formed by two, three and five tubular segments. Numerical simulations were performed considering a tumour located in the bile duct, where two important blood vessels – the portal vein and the hepatic artery – have a significant impact due to the convective heat transfer caused by the blood flow (heat sink effect) which significantly affects the shape of lesion that is intended to induce in order to destroy the tumour.

The results obtained show that the five-segment electrode arrangement allows a regular volume for the induced lesion, independently of the different values of applied voltage considered.

The presented work introduces a numerical simulation analysis on a modified based-stent electrode previously studied. In this case, the electrode is configured so it can be used as a bipolar electrode, i.e., active and ground electrode are placed in the same device. Besides the results evinced by the obtained results, this kind of electrode avoids eventual skin burns that might occur due to the need of the return electrodes when monopolar electrodes are used.

This paper aims to investigate the processability by selective laser melting (SLM) of materials of potential interest for innovative biodegradable implants, pure Fe and pure Zn. The processability of these materials is evaluated with a more established counterpart in permanent implants, stainless steel. In particular, the processing conditions were studied to reduce porosity due to incomplete fusion of the powder.

In the first phase of the experiments, SLM of AISI 316L was studied through design of experiments method. The study was used to identify the significant parameters in the experimental range and estimate the fluence ranges for pure Fe and pure Zn using the lumped heat capacity model. In the second phase, SLM of pure Fe and pure Zn were studied using estimated fluence ranges. In the final phase, best conditions were characterized for mechanical properties.

The results showed that complete melting of AISI 316L and pure Fe could be readily achieved, whereas laser melting generated a foam-like porous structure in Zn samples. The mechanical properties of laser melt implant materials were compared to as-cast and rolled counterparts. Laser melted AISI 316L showed superior mechanical performance compared to as-cast and rolled material, whereas Fe showed mechanical performance similar to rolled mild steel. Despite 12 per cent apparent porosity, laser melted Zn exhibited superior mechanical properties compared to as-cast and wrought material because of reduced grain size.

The paper provides key processing knowledge on the SLM processability of new biodegradable metals, namely, pure Fe, which has been studied sparingly, and pure Zn, on which no previous work is available. The results prefigure the production of new biodegradable metallic implants with superior mechanical properties compared to their polymeric counterparts and with improved degradation rates compared to magnesium alloys, the reference material for biodegradable metals.

A review on additive manufacturing (AM) of shape memory polymer composites (SMPCs) is put forward to highlight the progress made up to date, conduct a critical review and show the limitations and possible improvements in the different research areas within the different AM techniques. The purpose of this study is to identify academic and industrial opportunities.

This paper introduces the reader to three-dimensional (3 D) and four-dimensional printing of shape memory polymers (SMPs). Specifically, this review centres on manufacturing technologies based on material extrusion, photopolymerization, powder-based and lamination manufacturing processes. AM of SMPC was classified according to the nature of the filler material: particle dispersed, i.e. carbon, metallic and ceramic and long fibre reinforced materials, i.e. carbon fibres. This paper makes a distinction for multi-material printing with SMPs, as multi-functionality and exciting applications can be proposed through this method. Manufacturing strategies and technologies for SMPC are addressed in this review and opportunities in the research are highlighted.

This paper denotes the existing limitations in the current AM technologies and proposes several directions that will contribute to better use and improvements in the production of additive manufactured SMPC. With advances in AM technologies, gradient changes in material properties can open diverse applications of SMPC. Because of multi-material printing, co-manufacturing sensors to 3D printed smart structures can bring this technology a step closer to obtain full control of the shape memory effect and its characteristics. This paper discusses the novel developments in device and functional part design using SMPC, which should be aided with simple first stage design models followed by complex simulations for iterative and optimized design. A change in paradigm for designing complex structures is still to be made from engineers to exploit the full potential of additive manufactured SMPC structures.

Advances in AM have opened the gateway to the potential design and fabrication of functional parts with SMPs and their composites. There have been many publications and reviews conducted in this area; yet, many mainly focus on SMPs and reserve a small section to SMPC. This paper presents a comprehensive review directed solely on the AM of SMPC while highlighting the research opportunities.