Development of Novel High Strength Biodegradable Metals for Temporary Biomedical Implants

摘要：生物医学设备行业的一个梦想是用能够在最初几个月内发挥其功能并在宿主体内溶解的支架取代永久性血管内支架，从而消除目前永久性支架所经历的有害的长期影响。本工作旨在克服生物可降解植入材料最具挑战性的一个方面，通过加工控制微观结构，以提高机械性能和控制生理环境中的寿命。这项工作的广泛影响包括使用先进的热机械加工方法来改善锌基生物可降解金属的机械性能。这种方法有可能改变生物可降解植入物的加工方式，并通过实施制造生物可降解植入物材料的新工艺，在生物医学行业引发一场革命。其他更广泛的影响包括生产锌合金加工-微观结构-性能关系的模块，扩大密歇根州立大学（MSU）建立的K-12动手基于sem的外展计划，并为研究生和本科生提供研究机会。这些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。总的来说，这项工作旨在通过了解锌合金的加工-显微组织-性能关系来产生持久的影响。技术摘要：由于锌（Zn）及其合金具有接近理想的生物腐蚀和生物相容性，因此在生物医学应用方面具有广阔的前景，例如生物可降解支架。然而，纯锌作为可吸收支架材料的主要缺点是缺乏机械强度。高压扭转和等径角挤压等强塑性变形技术可以显著提高Zn合金的强度，使其微观组织得到显著改善。SPD技术在金属基纳米复合材料（mmnc）中的应用尤其有前景。虽然以锌为基质的mmnc还处于起步阶段，但它们有可能产生具有增强强度的可生物降解材料，同时保持生物腐蚀行为和生物相容性，对可生物降解植入物具有吸引力。总体而言，该项目将评估锌基mmnc作为可生物降解植入物的可行性，并将测试新型SPD方法用于晶粒细化。这项工作的重点将是了解这些材料的加工-微观结构-性能关系。此外，与标准的可生物降解锌合金相比，将了解这些材料的腐蚀行为和机制以及生物相容性的性质。

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.