GOALI/Collaborative Research: Thixotropic Metal Processing and 3D Printing of Zinc-Magnesium Bio-Alloys for Biomedical Implant Applications

该奖项支持基础研究，以探索能够3D打印锌镁生物合金的新型制造系统。这些合金由于其生物降解性和高强度而在植入式医疗装置中是非常理想的。然而，这些生物合金的粉末熔融3D打印非常难以控制，因为在高功率激光下会发生汽化和氧化。由于没有锌镁生物合金的直接印刷工艺，几乎不可能制造定制设备。为了克服这一障碍，一种新的触变3D打印方法可以控制粘度，使锌镁生物合金可以通过挤出工艺直接打印成精确的定制3D形状。这项新技术有望使骨骼和软组织固定工具、血管膨胀支架和骨组织支架受益。这将通过提供坚固且可在体内生物降解/可吸收的患者定制医疗器械来改善矫形、脊柱和血管手术。该新工艺也可适用于制造用于其他工业应用的铝基合金。该项目将用于教育推广活动，特别是针对初中/高中和代表性不足的少数民族学生，展示高科技生物制造，生物材料及其外科工程应用。熔融合金具有低粘度但高表面张力，使得稳定的3D打印几乎不可能。假设通过触变加工可以为锌镁生物合金创建具有细球形形态的两相微浆料，并且这可以有效地使浆料适合于通过挤出进行3D打印。为了验证这一假设并建立该方法的技术可行性，将开展三项研究任务：1）对触变挤压和打印中的合金设计、形态形成、触变性与可打印性之间的关系以及加工、结构和性能之间的关系进行基础研究; 2）研究过程动力学并开发触变3D打印的建模能力; 3）建立用于锌镁生物合金的自由成形制造的实验室设置。研究人员将获得新的触变金属成形和3D打印方法以及新的锌镁生物合金的独特加工-结构-性能关系的基本了解。特别是在以下领域期待新的科学知识：a）在半固态金属加工中促进合金触变性的机理; B）合金高应力混合中的流体力学和流变学; c）半固态沉积中触变性和可印刷性之间的基本关系;以及d）处理的基本关系，新型锌镁生物可降解材料结构与性能该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This Grant Opportunity for Academic Liaison with Industry (GOALI) award supports fundamental research to explore a novel manufacturing system that is capable of 3D printing zinc-magnesium bio-alloys. These alloys are highly desirable in implanted medical devices for their biodegradability and high strength. However, powder fusion 3D printing of these bio-alloys is very difficult to control because of vaporization and oxidization under high power laser. Not having a direct printing process for zinc-magnesium bio-alloys makes it nearly impossible to manufacture custom devices. To overcome this hurdle, a new thixotropic 3D printing methodology in which the viscosity is controlled, could allow zinc-magnesium bio-alloys to be directly printed via an extrusion process into accurate, customized 3D shapes. The new technology is expected to benefit skeletal and soft tissue fixation tools, vascular inflation stents, and bone tissue scaffolds. This would lead to improvements in orthopedic, spinal and vascular surgery by providing patient-tailored medical devices that are strong and biodegradable/absorbable in the body. The new process may also be adapted to the fabrication of aluminum-based alloys for other industrial applications. The project will be used in educational outreach activities, especially to middle/high school and underrepresented minority students, to showcase high-tech bio-fabrication, biomaterials, and their surgical engineering applications.Molten alloys have low viscosity but high surface tension, making stable 3D printing nearly impossible. It is hypothesized that a two-phase micro-slurry with a fine globular morphology can be created for zinc-magnesium bio-alloys by thixotropic processing, and this can effectively make the slurry suitable for 3D printing by extrusion. Three research tasks will be performed to test this hypothesis and establish the technical feasibility of the method: 1) Conduct basic research on alloy design, morphological formation, relation between thixotropy and printability, and relation of processing, structure and property in thixotropic extrusion and printing; 2) Study the process dynamics and develop modeling capability for thixotropic 3D printing; 3) Establish a laboratory setup for freeform fabrication of zinc-magnesium bio-alloys. Researchers will obtain fundamental understanding of the unique processing-structure-property relationships of the new thixotropic metal forming and 3D printing methods and the new zinc-magnesium bio-alloy. New scientific knowledge is particularly anticipated in the following areas: a) mechanisms of promoting thixotropy of alloys in semi-solid metal processing; b) fluid mechanics and rheology in high-stress mixing of alloys; c) fundamental relationships between thixotropy and printability in semi-solid-state deposition; and d) fundamental relationships of processing, structure and property regarding biodegradability and performance of a new zinc-magnesium bio-alloy.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.