Mechanical analysis of radial performance in biodegradable polymeric vascular stents manufactured using micro-injection molding

Micro-injection molding (MiM) is a promising technique for manufacturing biodegradable polymeric vascular stents (BPVSs) at scale, in which a trapezoidal strut cross section is needed to ensure high-quality de-molding. However, there is a lack of research on the influence of the strut cross-sectional shape on its mechanical properties, posing a challenge in determining the key geometries of the strut when using MiM to produce BPVSs. Hence, this work has investigated the relationships between the geometry parameters, including the de-molding angle, and the radial support property of BPVSs using the finite element method. The results reveal that the radial stiffness of BPVSs is significantly affected by the de-molding angle, which can be counteracted by adjusting strut height, bending radius, and strut thickness. Stress distribution analysis underscores the crucial role of the curved portion of the support ring during compression, with the inner side of the curved region experiencing stress concentration. A mathematical model has been established to describe the relationships between the geometry parameters and the radial support property of the BPVSs. Notably, the radius of the neutral layer emerges as a key determinant of radial stiffness. This study is expected to serve as a guideline for the development of BPVSs that can be manufactured using MiM.

An Innovative Stereolithography 3D Tubular Method for Ultrathin Polymeric Stent Manufacture: The Effect of Process Parameters

In the last decades, researchers have been developing bioresorbable stents (BRS) to overcome the long-term complications of drug-eluting stents (DES). However, BRS technology still presents challenging limitations in terms of manufacturing, materials, or mechanical properties. At this juncture, companies have developed ultrathin DES that may further improve the efficacy and safety profile of traditional DES by reducing the risk of target-lesion and target-vessel failures until BRS are developed. Nonetheless, the metallic platform of ultrathin DES still presents problems related to their cellular response. The use of polymers as a permanent platform in DES has not previously been studied due to the limitations of current manufacturing technologies. In this work, an innovative manufacturing method for polymeric stent production using tubular stereolithography (SLA) technology is proposed both for BRS and for ultrathin polymeric DES. The effects of manufacturing process parameters were studied by modelling the outcomes (stent thickness and strut width) with the key manufacturing variables (exposure, resin volume, and number of layers). Two different laser setups were used to compare the results. Microscopy results proved the merit of this novel tubular SLA process, which was able to obtain stents with 70 μm strut width and thickness in barely 4 min using only 0.2 mL of resin. Differential Scanning Calorimetry (DSC) results showed the stability of the manufacturing method. The results obtained with this innovative technology are promising and overcome the limitations of other previously used and available technologies.

Development of Biodegradable Polymeric Stents for the Treatment of Cardiovascular Diseases

Cardiovascular disease has become the leading cause of death. A vascular stent is an effective means for the treatment of cardiovascular diseases. In recent years, biodegradable polymeric vascular stents have been widely investigated by researchers because of its degradability and clinical application potential for cardiovascular disease treatment. Compared to non-biodegradable stents, these stents are designed to degrade after vascular healing, leaving regenerated healthy arteries. This article reviews and summarizes the recent advanced methods for fabricating biodegradable polymeric stents, including injection molding, weaving, 3D printing, and laser cutting. Besides, the functional modification of biodegradable polymeric stents is also introduced, including visualization, anti-thrombus, endothelialization, and anti-inflammation. In the end, the challenges and future perspectives of biodegradable polymeric stents were discussed.

Material Extrusion Advanced Manufacturing of Helical Artificial Muscles from Shape Memory Polymer

Rehabilitation and mobility assistance using robotic orthosis or exoskeletons have shown potential in aiding those with musculoskeletal disorders. Artificial muscles are the main component used to drive robotics and bio-assistive devices. However, current fabrication methods to produce artificial muscles are technically challenging and laborious for medical staff at clinics and hospitals. This study aims to investigate a printhead system for material extrusion of helical polymer artificial muscles. In the proposed system, an internal fluted mandrel within the printhead and a temperature control module were used simultaneously to solidify and stereotype polymer filaments prior to extrusion from the printhead with a helical shape. Numerical simulation was applied to determine the optimal printhead design, as well as analyze the coupling effects and sensitivity of the printhead geometries on artificial muscle fabrication. Based on the simulation analysis, the printhead system was designed, fabricated, and operated to extrude helical filaments using polylactic acid. The diameter, thickness, and pitch of the extruded filaments were compared to the corresponding geometries of the mandrel to validate the fabrication accuracy. Finally, a printed filament was programmed and actuated to test its functionality as a helical artificial muscle. The proposed printhead system not only allows for the stationary extrusion of helical artificial muscles but is also compatible with commercial 3D printers to freeform print helical artificial muscle groups in the future.

3D Printing of Polymeric Bioresorbable Stents: A Strategy to Improve Both Cellular Compatibility and Mechanical Properties

One of the leading causes of death is cardiovascular disease, and the most common cardiovascular disease is coronary artery disease. Percutaneous coronary intervention and vascular stents have emerged as a solution to treat coronary artery disease. Nowadays, several types of vascular stents share the same purpose: to reduce the percentage of restenosis, thrombosis, and neointimal hyperplasia and supply mechanical support to the blood vessels. Despite the numerous efforts to create an ideal stent, there is no coronary stent that simultaneously presents the appropriate cellular compatibility and mechanical properties to avoid stent collapse and failure. One of the emerging approaches to solve these problems is improving the mechanical performance of polymeric bioresorbable stents produced through additive manufacturing. Although there have been numerous studies in this field, normalized control parameters for 3D-printed polymeric vascular stents fabrication are absent. The present paper aims to present an overview of the current types of stents and the main polymeric materials used to fabricate the bioresorbable vascular stents. Furthermore, a detailed description of the printing parameters' influence on the mechanical performance and degradation profile of polymeric bioresorbable stents is presented.

A Review on Manufacturing and Post-Processing Technology of Vascular Stents

Percutaneous coronary intervention (PCI) with stent implantation is one of the most effective treatments for cardiovascular diseases (CVDs). However, there are still many complications after stent implantation. As a medical device with a complex structure and small size, the manufacture and post-processing technology greatly impact the mechanical and medical performances of stents. In this paper, the development history, material, manufacturing method, and post-processing technology of vascular stents are introduced. In particular, this paper focuses on the existing manufacturing technology and post-processing technology of vascular stents and the impact of these technologies on stent performance is described and discussed. Moreover, the future development of vascular stent manufacturing technology will be prospected and proposed.

3D printing advances in the development of stents

3D printing technologies have found several applications within the biomedical sector including in the fabrication of medical devices, advanced visualization, diagnosis planning and simulation of surgical procedures. One of the areas in which of 3D printing is anticipated to revolutionised is the manufacturing of implantable bioresorbable drug-eluting scaffolds (stents). The ability to customize and create personalised tailor-made bioresorbable scaffolds has the potential to help solve many of the challenges associated with stenting, such as inappropriate stent sizing and design, abolish late stent thrombosis and help artery growth; 3D printing offers a rapid prototyping and effective method of producing stents making customization of designs feasible. This review provides an overview of the subjects and summarizes the latest research in the 3D printing technologies employed for the design and fabrication of bioresorbable stents including materials with the required printable and mechanical properties. Finally, we present a regulatory perspective on the development and engineering of 3D printed implantable stents.

Structural Design of Vascular Stents: A Review

Percutaneous Coronary Intervention (PCI) is currently the most conventional and effective method for clinically treating cardiovascular diseases such as atherosclerosis. Stent implantation, as one of the ways of PCI in the treatment of coronary artery diseases, has become a hot spot in scientific research with more and more patients suffering from cardiovascular diseases. However, vascular stent implanted into vessels of patients often causes complications such as In-Stent Restenosis (ISR). The vascular stent is one of the sophisticated medical devices, a reasonable structure of stent can effectively reduce the complications. In this paper, we introduce the evolution, performance evaluation standards, delivery and deployment, and manufacturing methods of vascular stents. Based on a large number of literature pieces, this paper focuses on designing structures of vascular stents in terms of “bridge (or link)” type, representative volume unit (RVE)/representative unit cell (RUC), and patient-specific stent. Finally, this paper gives an outlook on the future development of designing vascular stents.

Continuous Based Direct Ink Write for Tubular Cardiovascular Medical Devices

Bioresorbable cardiovascular applications are increasing in demand as fixed medical devices cause episodes of late restenosis. The autologous treatment is, so far, the gold standard for vascular grafts due to the similarities to the replaced tissue. Thus, the possibility of customizing each application to its end user is ideal for treating pathologies within a dynamic system that receives constant stimuli, such as the cardiovascular system. Direct Ink Writing (DIW) is increasingly utilized for biomedical purposes because it can create composite bioinks by combining polymers and materials from other domains to create DIW-printable materials that provide characteristics of interest, such as anticoagulation, mechanical resistance, or radiopacity. In addition, bioinks can be tailored to encounter the optimal rheological properties for the DIW purpose. This review delves into a novel emerging field of cardiovascular medical applications, where this technology is applied in the tubular 3D printing approach. Cardiovascular stents and vascular grafts manufactured with this new technology are reviewed. The advantages and limitations of blending inks with cells, composite materials, or drugs are highlighted. Furthermore, the printing parameters and the different possibilities of designing these medical applications have been explored.