Abstract Laser powder bed fusion (LPBF) is one of the most popular metal additive manufacturing technologies, which has found its applications in high-value sectors such as aerospace and biomedical devices. Some recent studies on the LPBF of stents have demonstrated its feasibility in the fabrication in thin strut structures including heart valve frames, as used in transcatheter aortic valve implantation (TAVI) for the treatment of severe aortic stenosis. The state of the art method of laser cutting TAVI frame limits the scope for novel concepts which are made possible by additive manufacturing. However, the surface quality and dimensional accuracy of LPBF parts are lower than that produced by laser cutting. To start the development of new TAVI concepts, the feasibility of manufacturing thin frames by LPBF has been investigated based the SAPIEN 3 frame by Edwards Lifesciences. In this study, simplified frames with strut size from 0.3 mm to 0.5 mm have been successfully manufactured. The effects of strut size, strut angle, laser power and scan speed on the dimensional accuracy and surface quality were systemically studied. In addition, a representative SAPIEN 3 frame was manufactured and assessed with high resolution X-ray scans. Good overall dimensional accuracy and low porosity was obtained for the SAPIEN 3 frame. However, inclined struts were found to have relatively low dimensional accuracy and poor surface quality.
Questo lavoro di tesi mira ad ottenere una catena di processo per realizzare microcomponenti gerarchici in materiale polimerico. In particolare vengono abbinate tra loro in maniera sinergica varie tecnologie, tra cui la litografia laser diretta di NanoScribe, la tecnologia Replica Moulding e il microstampaggio ad iniezione. Vengono ottimizzati i parametri di processo di ogni tecnologia, e caratterizzate le strutture ottenute.
Abstract Laser powder bed fusion (LPBF) is one of the most popular metal additive manufacturing technologies, which has found its applications in high-value sectors such as aerospace and biomedical devices. Some recent studies on the LPBF of stents have demonstrated its feasibility in the fabrication in thin strut structures including heart valve frames, as used in transcatheter aortic valve implantation (TAVI) for the treatment of severe aortic stenosis. The state of the art method of laser cutting TAVI frame limits the scope for novel concepts which are made possible by additive manufacturing. However, the surface quality and dimensional accuracy of LPBF parts are lower than that produced by laser cutting. To start the development of new TAVI concepts, the feasibility of manufacturing thin frames by LPBF has been investigated based on the SAPIEN 3 frame by Edwards Lifesciences. In this study, simplified frames with strut size from 0.3 to 0.5 mm have been successfully manufactured. The effects of strut size, strut angle, laser power and scan speed on the dimensional accuracy and surface quality were systemically studied. In addition, a representative SAPIEN 3 frame was manufactured and assessed with high-resolution X-ray CT scans. Good overall dimensional accuracy and low porosity were obtained for the SAPIEN 3 frame. However, inclined struts were found to have relatively low dimensional accuracy and poor surface quality.
Since additive manufacturing (AM) technology first emerged in the late 1980s, the medical sector has benefited from AM due to the advantages of high design flexibility, mass customization ability, and manufacturability for complex structures. Further, recent developments in metal AM technologies have led to the presence of increasing numbers of AM devices on the market. This article provides an overview of the state of the art in metal AM technologies for the medical sector, including metal AM techniques and typical systems, biometallic materials, design considerations for AM and post treatment of AM parts. Furthermore, several current applications of metal AM devices are discussed in the dental industry, maxillofacial implants and orthopaedics. The general workflow for patient specific device design is also addressed. Despite these advances, there are several constraints on continued rapid growth of metal AM devices in clinical practice. Attention is herein given, therefore, to the challenges for regulatory approval, limited understanding of long-term clinical outcomes and the effects of AM defects. It is hoped that inter-disciplinary advances in AM, materials and design will lead to the continued growth in metal AM biomedical device development. The article concludes with recommendations for possible AM devices that could be developed for new applications, e.g. cardiovascular engineering applications.
Typically, the frames of replacement heart valves are manufactured by laser cutting. Whilst this method limits the scope for novel concepts are made possible by additive manufacturing. With this in mind, the feasibility of manufacturing heart valve frames by laser powder bed fusion (LPBF) has been investigated based the SAPIEN 3 frame. Using stainless steel powder, this study has demonstrated the feasibility of successfully manufacturing frames with 0.4 mm cross-sectional dimensions. Although geometric accuracy and surface quality need to be improved, a low porosity of 0.5% was achieved and the frames could be successfully crimped and expanded without any breakages.
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