The Fundamental Study of Nanoparticle Effects in Metal Matrix Nanocomposite for Biomedical Applications

Metals have been widely used for biomedical applications, especially as bio-implants, due to their excellent mechanical properties that are suitable for load-bearing applications. Zn has recently attracted attention for being used as biodegradable materials for implants, especially for bioresorbable stent and biodegradable electrodes. The suitable corrosion rate and benign biocompatibility promote Zn as a potential candidate for bioresorbable cardiovascular stents. However, the lack of strength and thermal stability inhibited its practical application and commercialization. Alloying has been applied for strengthening but inevitably introducing side-effects, such as increased corrosion rate and decreased elongation. In this dissertation, a new class of materials, metal matrix nanocomposite, was investigated for biomedical applications, including biodegradable implants (e.g., bioresorbable cardiovascular stents) and medical devices (e.g., degradable nanowire biosensors). In the beginning, this work has developed and optimized the fabrication methods of Zn matrix nanocomposite, enabling efficient nanoparticle incorporation and homogeneous dispersion. Additionally, through the characterization in microstructure and mechanical properties, this work has thoroughly investigated the nanoparticle interaction with the grain boundaries and intermetallic interfaces during the solidification process and aging process. Furthermore, this work has characterized the mechanical properties of Zn-based nanocomposites and has fabricated the prototype of bioresorbable stents for evaluation. For the application of biodegradable electrodes consisting of metal nanowires, nanoparticles have enabled molten metal viscosity/interfacial energy modification and fluid instability suppression to realize the high aspect ratio nanowire fabrication. This dissertation successfully establishes fundamental knowledge for metal matrix nanocomposite as suitable biomaterials for various medical applications, bridging the advanced manufacturing of novel biometals to innovative biomedical devices and providing innovative solutions for human health