Development of Novel High Strength Biodegradable Metals for Temporary Biomedical Implants

非技术摘要：生物医疗器械行业的一个梦想是用支架取代永久性血管内支架，这种支架可以在最初几个月发挥其功能，然后在宿主体内溶解，消除目前永久支架所经历的有害的长期影响。这项工作旨在克服可生物降解植入材料最具挑战性的方面之一，通过加工来控制微结构，以提高机械性能并控制生理环境中的寿命。这项工作的更广泛影响包括使用先进的热机械加工方法来改善锌基可生物降解金属的机械性能。这种方法有可能改变可生物降解植入物的加工方式，并通过实施制造可生物降解植入物材料的新工艺，在生物医学行业引发一场革命。拟议工作的其他更广泛影响包括制作锌合金加工-显微结构-性能关系的模块，扩大密歇根州立大学(MSU)基于K-12实践扫描电子显微镜的扩展计划，以及为研究生和本科生提供研究机会。该模块和推广计划旨在帮助促进K-12学生进入科学、技术、工程和数学(STEM)学科。技术摘要：由于锌及其合金表现出接近理想的生物腐蚀和生物相容性，锌及其合金在生物医学领域的应用前景看好，例如生物可降解支架。然而，纯锌作为可吸收支架材料的一个主要缺点是缺乏机械强度。通过高压扭转和等通道转角挤压等严重塑性变形(SPD)技术可以显著提高锌合金的强度，这两种技术都可以显著细化组织。这样的SPD技术在金属基纳米复合材料(MMNC)中的应用尤其有前景。尽管以锌为基质的MMNCs还处于起步阶段，但它们有可能在保持生物腐蚀行为和生物相容性的同时，产生具有更高强度的可生物降解材料。总体而言，该计划将评估锌基MMNC作为可生物降解植入物的可行性，并将测试用于细化颗粒的新型SPD方法。这项工作的重点将是了解这些材料的加工-组织-性能关系。此外，还将与标准的可生物降解锌合金相比较，了解这些材料的腐蚀行为和机理以及生物相容性的本质。

Non-Technical Abstract: A dream of the biomedical devices industry is to replace permanent endovascular stents with stents that can perform their function in the first few months and then dissolve in the host body, eliminating harmful long-term effects experienced with current permanent stents. This work seeks to overcome one of the most challenging aspects of biodegradable implant materials, controlling the microstructure, through processing, for enhancing the mechanical behavior and controlling the lifetime in physiological environments. The broader impacts of this work include use of the advanced thermomechanical processing methods to improve the mechanical properties of zinc-based biodegradable metals. This approach has the potential to change how biodegradable implants are processed and can initiate a revolution in the biomedical industry by implementing new processes for manufacturing biodegradable implants materials. Other broader impacts of the proposed work include producing modules on processing-microstructure-property relationships of zinc alloys, expanding an established K-12 hands-on SEM-based outreach program at Michigan State University (MSU), and providing research opportunities for graduate and undergraduate students. The modules and outreach program are intended to help promote K-12 students to enter Science, Technology, Engineering and Math (STEM) disciplines. Overall, this work is intended to make a lasting effect by understanding processing-microstructure-property relationships of zinc alloys.Technical Abstract:Because they exhibit near-ideal biocorrosion and biocompatibility behavior, zinc (Zn) and its alloys show promise for biomedical applications such as biodegradable stents. However, a primary drawback of pure Zn as an absorbable stent material is the lack of mechanical strength. The strengths of Zn alloys can be significantly improved through severe plastic deformation (SPD) techniques such as high-pressure torsion and equal channel angular pressing, both of which result in a significantly refined microstructure. The application of SPD techniques, such as these, is especially promising for metal matrix nanocomposites (MMNCs). Although MMNCs containing Zn as a matrix is in its infancy, they have the potential to result in biodegradable materials with enhanced strengths, while maintaining biocorrosion behavior and biocompatibility attractive for biodegradable implants. Overall, this program will evaluate the viability of Zn-matrix MMNCs as biodegradable implants and will test the novel SPD approach for grain refinement. A focus of this work will be to understand processing-microstructure-property relations of these materials. In addition, an understanding of the corrosion behavior and mechanisms and the nature of the biocompatibility of these materials in comparison to standard biodegradable Zn alloys will be obtained.