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

这一学术联系机会奖(GOALI)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。这些合金因其可生物降解性和高强度而在植入式医疗设备中非常受欢迎。然而，由于这些生物合金在高功率激光作用下会发生汽化和氧化，粉末熔融3D打印很难控制。没有锌镁生物合金的直接打印工艺，几乎不可能制造定制的设备。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压工艺直接打印成准确的、定制的3D形状。这项新技术预计将有利于骨骼和软组织固定工具、血管充气支架和骨组织支架。这将通过提供坚固且可在体内生物降解/吸收的患者定制的医疗设备来改进整形外科、脊柱和血管手术。新工艺也可用于其他工业用途的铝基合金的制造。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族裔学生，以展示高科技生物制造、生物材料及其外科工程应用。熔化的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制备出具有良好球状形貌的两相微浆料，这将有效地使浆料适合于挤压3D打印。为了验证这一假设并建立该方法的技术可行性，将进行三项研究任务：1)对触变挤压和印刷中的合金设计、形态形成、触变性与印刷适性的关系以及工艺、结构和性能的关系进行基础研究；2)研究触变3D印刷的过程动力学和开发建模能力；3)建立锌镁生物合金自由形状制造的实验室装置。研究人员将从根本上了解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工艺-结构-性能关系。新的科学知识在以下领域尤其值得期待：a)在半固态金属加工中促进合金触变性的机制；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与印刷适宜性之间的基本关系；以及d)关于新型锌镁生物合金的生物降解性和性能的加工、结构和性能的基本关系。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.