135 research outputs found
Advantages of additive manufacturing for biomedical applications of polyhydroxyalkanoates
In recent years, biopolymers have been attracting the attention of researchers and special-ists from different fields, including biotechnology, material science, engineering, and medicine. The reason is the possibility of combining sustainability with scientific and technological progress. This is an extremely broad research topic, and a distinction has to be made among different classes and types of biopolymers. Polyhydroxyalkanoate (PHA) is a particular family of polyesters, synthetized by microorganisms under unbalanced growth conditions, making them both bio-based and biodegradable polymers with a thermoplastic behavior. Recently, PHAs were used more intensively in biomedical applications because of their tunable mechanical properties, cytocompatibility, adhesion for cells, and controllable biodegradability. Similarly, the 3D-printing technologies show increasing potential in this particular field of application, due to their advantages in tailor-made design, rapid prototyping, and manufacturing of complex structures. In this review, first, the synthesis and the production of PHAs are described, and different production techniques of medical implants are compared. Then, an overview is given on the most recent and relevant medical applications of PHA for drug delivery, vessel stenting, and tissue engineering. A special focus is reserved for the inno-vations brought by the introduction of additive manufacturing in this field, as compared to the traditional techniques. All of these advances are expected to have important scientific and commer-cial applications in the near future
Novel PBAT-Based Biocomposites Reinforced with Bioresorbable Phosphate Glass Microparticles
Biocomposites based on poly(butylene adipate terephthalate) (PBAT) and reinforced with micro-particles of inorganic biodegradable phosphate glass (PG) at 2, 10, and 40 wt% are prepared and characterized from a mechanical and morphological point of view. Scanning electron microscope (SEM) images show a good dispersion of the PG micro-grains, even at high concentrations, in the PBAT matrix, resulting in homogeneous composites. Tensile and dynamic-mechanical tests, respectively, indicate that Young's and storage moduli increase with PG concentration. The reinforcement of PBAT aims at modifying and tailoring the mechanical and viscoelastic properties of the material to expand its application field especially in the food and agricultural packaging sector, thanks to the similarity of PBAT performance with polyethylene
Benchmarking analysis of digital light processing resins in terms of dimensional accuracy and geometric tolerances
Additive Manufacturing (AM) is a groundbreaking fabrication technology that is revolutionizing traditional manufacturing processes. Generally, following a layer-by-layer approach, in AM the final shape of the product is built through the progressive deposition of one or more materials. The most common extrusion-based AM technique for thermoplastic polymers is Fused Filament Fabrication (FFF), whilst for photopolymer resins, Digital Light Processing (DLP) and Stereolithography (SLA) are widely used. In the last years, DLP has spread rapidly, due to its low average cost and simple use. Moreover, a lower layer thickness can be used in DLP if compared to the FFF process. Therefore, hobbyists or amateur end users and many companies use DLP to achieve high dimensional accuracy and smooth surfaces for small products.
This work aims to evaluate the performance of three different DLP resins in terms of dimensional and geometrical accuracy. A benchmarking activity is carried out using a Rover printer by Sharebot to produce replicas of a reference part using Sharebot resins. After production, the replicas were inspected using a Coordinate Measuring Machine (CMM) for comparing the dimensional accuracy of the geometric features according to ISO IT grades and tolerances of the GD&T system. The results of this study are also compared with previous works from the literature in the conclusions
Novel 3D printable bio-based and biodegradable poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) microspheres for selective laser sintering applications
Selective laser sintering (SLS) has become the most popular additive manufacturing process due to its high accuracy, productive efficiency, and surface quality. However, currently there are still very few commercially available polymeric materials suitable for this technique. This research work focused on the fabrication and characterization of bio-based and biodegradable microspheres obtained by oil-in-water emulsion solvent evaporation, starting from a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) biopolymer matrix. First, the fabrication parameters were optimized to improve the morphological, thermal, and flowability properties of the synthetized microspheres. Once the best production conditions were established, the PHBH microspheres were further used to study their effective 3D printability on an SLS 3D printer using geometries varying from simple shapes to architectures with more complex internal patterns. The results of this research revealed that PHBH has promising applicability for the SLS technique. This study undertook the first step toward broadening the range of polymeric materials for this additive manufacturing technology. These findings will contribute to a greater and wider dissemination of the SLS technique in the future, as well as they will bring this manufacturing process closer to applications, such as the biomedical sector, where the use of biodegradable and biocompatible materials can add value to the final application
An approach to evaluate the wear of customized manufacturing fixtures through the analysis of 3D scan data
With the recent gain in popularity and adoption of additive manufacturing in various industrial sectors, quality assessments to determine the functionality of 3D printed parts are critical. This holds especially when the parts are subjected to wear as in the case of the production of customized fixtures. Some reinforced polymeric materials for additive manufacturing can be employed as a substitute for low-resistance metals like Aluminium. In this paper, a custom-made tribometer was used to simulate the wear of 3D printed fixtures of Alumide material for sheet metal inspection operations. Contact 3D scanning is used to monitor the condition of the fixture for increasing numbers of wear cycles. This study aims to calculate the wear volume of cylindrical pins starting from the surface points of 3D scan data. The methodology employs alpha shapes to obtain the progression of the volume and area of the worn zone. Experimental tests to evaluate the wear volume were carried out to compare the durability of Alumide to that of Aluminium, filling the gap of previous literature, which had focused exclusively on diametral wear. The findings indicate a better wear resistance for Alumide specimens and this work contributes to broadening the knowledge about the wear behaviour and the lifetime of 3D printed parts
Chapter 9 Moral Responsibility and the Justification of Policies to Preserve Antimicrobial Effectiveness
Restrictive policies that limit antimicrobial consumption, including therapeutically
justified use, might be necessary to tackle the problem of antimicrobial
resistance. We argue that such policies would be ethically justified when forgoing
antimicrobials constitutes a form of easy rescue for an individual. These are cases
of mild and self-limiting infections in otherwise healthy patients whose overall
health is not significantly compromised by the infection. In such cases, restrictive
policies would be ethically justified because they would coerce individuals into fulfilling
a moral obligation they independently have. However, to ensure that such
justification is the strongest possible, states also have the responsibility to ensure
that forgoing antimicrobials is as easy as possible for patients by implementing
adequate compensation measures
Antimicrobial Footprints, Fairness, and Collective Harm
This chapter explores the question of whether or not individual agents
are under a moral obligation to reduce their ‘antimicrobial footprint’. An agent’s
antimicrobial footprint measures the extent to which her actions are causally linked
to the use of antibiotics. As such, it is not necessarily a measure of her contribution
to antimicrobial resistance. Talking about people’s antimicrobial footprint in a way
we talk about our carbon footprint may be helpful for drawing attention to the global
effects of individual behaviour and for highlighting that our choices can collectively
make a real difference. But can we be morally obligated to make a contribution to
resolving a collective action problem when our individual contributions by themselves
make no discernible difference? I will focus on two lines of argument in
favour of such obligations: whether a failure to reduce one’s antimicrobial footprint
is unfair and whether it constitutes wrongdoing because it is harmful. I conclude by
suggesting that the argument from collective harm is ultimately more successful
The moral obligation to be vaccinated: utilitarianism, contractualism, and collective easy rescue
Despite the success of vaccines in preventing and sometimes eradicating infectious diseases, and despite their demonstrated safety (Navin 2015, p. 6; CDC 2015a; Andre et al 2008), many people today refuse vaccination for themselves or their children. In the U.S. there has been a significant increase in cases of measles over the last few years due to increasingly widespread non-vaccination: in 2014, for example, there were 667 reported cases, the highest number since measles elimination was documented in the U.S. in 2000 (CDC 2016a). Similarly, in different parts of Europe there were measles outbreaks in 2016 and 2017, due to a significant decrease in measles vaccination rates; for example, in Italy there were more than 3,300 cases of measles in the first half of 2017, 88% of which were not vaccinated and 7% of which received just one dose of vaccine (ECDC 2017). Before the introduction of the measles vaccination program in 1963, 3-4 million people in the US were infected by measles every year, and 4-500 of them died (CDC, 2015b)
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