Functionally Graded Orthopedic Implants via the Slurry Mixing and Dispensing Process

用于骨折内固定和关节置换的材料目前都是金属制成的。然而，金属种植体有两个缺点，一是金属表面与周围骨之间的界面结合不良或不存在，二是金属种植体的硬度高于自然骨。因此，金属植入物的预期寿命与接受者的预期寿命不相称，必须每12-15年进行一次翻修手术。然而，手术翻修手术的费用可能是初次手术的两倍，并可能导致严重的并发症，包括感染、畸形、疼痛和失去活动能力。这项研究项目就是为了解决这些问题而提出的。智力优势：通过工程学和生命科学的创新集成，将研究和开发具有工程微结构层次的新型功能梯度、多孔的Ti-6Al-4V/磷灰石植入材料家族。这一新的骨科植入物系列是同类植入物中的第一个，因为它们具有富含钛的核心和富含羟基磷灰石(HA)的表面，并控制微孔和宏孔的水平。这些精心设计的成分梯度和工程微结构将赋予骨科植入物优异的耐腐蚀性、足够的强度、增强的机械兼容性和良好的生物活性，以促进骨组织再生和植入物的固定。这些革命性的功能分级整形植入物将为目前无论是否有涂层的金属植入物所面临的所有问题提供无与伦比的解决方案。一种新的固体自由形状制造(SFF)方法，被称为浆料混合和分配(SMD)工艺，用于制造功能梯度材料(FGM)，以制造这种新的骨科植入物家族。通过SMD工艺生产的绿色骨科植入物将使用我们实验室最近开发的一种新的烧结方法转化为固体植入物。这种新的烧结方法以羟基磷灰石纳米棒为起始粉末，在低至8500℃的烧结温度下获得致密的羟基磷灰石颗粒，这是文献中报道的最低温度。我们选择髋关节植入物作为研究和展示这一新的骨科生物材料家族的载体，因为髋部骨折是迄今为止最具破坏性的骨折类型，在美国每年约有30万人因髋部骨折而住院。为了实现研究目标，已经确定了五项技术任务，并组建了一支拥有所有必要专业知识的研究团队。我们坚信，这个研究团队的协同作用将使我们能够成功地进行这一多学科的项目，并推动骨科生物材料领域的前沿。广泛的影响：如果成功，该项目将产生良好的社会和经济影响，因为许多患者将从这项新技术中受益。患者的生活质量可以得到极大的提高。此外，减少翻修手术的需要可以转化为医疗保健成本的降低。此外，这项研究中开发的SMD工艺在未来可以应用于制造其他整形外科植入物(例如，脊柱固定装置、颌面部植入物、填充肿瘤缺陷的骨移植材料等)。以及许多其他功能梯度材料的广泛应用，如梯度折射率透镜、梯度装甲材料、燃料电池的双极板以及航空航天、汽车和工具工业的先进纳米复合材料。该计划的广泛影响也将体现在我们对教育、人力资源开发和外展的坚定承诺上，这将对本科生、研究生和初中生产生直接影响。我们将与康涅狄格州工程前期计划(CPEP)合作，增加工程、科学和技术领域代表性不足的少数族裔的数量。我们将在暑期接待CPEP学生，为他们提供与SMD制造和矫形植入物相关的动手实验室。将开发迷你项目，以便CPEP学生可以在研究生和PI的帮助下在一周内完成这些迷你项目。通过这项新举措，我们将培养代表不足的少数群体积极思考，提高他们对科学技术的兴趣，并激励他们接受高等教育，成为未来社会的领导者。

0930365ShawThe materials used for internal fracture fixations and joint replacements are all currently made of metals. However, metallic implants suffer from two shortcomings, one being the poor or non-existent interfacial bonding between the metallic surface and surrounding bone, and the other the higher rigidity of metallic implants than that of natural bone. As a result, the life expectancy of metallic implants is not commensurate with the life expectancy of the recipient, and revision surgery has to be performed every 12-15 years. Surgical revision, however, can be twice as expensive as the primary operation and may lead to significant complications, including infection, deformity, pain, and loss of mobility. This research project is proposed to address these issues.Intellectual Merit: A new family of functionally graded, porous Ti-6Al-4V/apatite implant materials with a hierarchy of engineered microstructures will be investigated and developed through innovative integration of engineering and life science. This new family of orthopedic implants is the first of its kind because they have a Ti-rich core and a hydroxyapatite (HA)-rich surface with a controlled level of micro- and macro-porosity. Together, these carefully designed composition gradients and engineered microstructures will impart to orthopedic implants the excellent corrosion resistance, adequate strength, enhanced mechanical compatibility, and good bioactivity for promoting bone tissue regeneration and fixation of implants. These revolutionary functionally graded orthopedic implants will offer an unparalleled solution to all of the issues faced by the present metallic implants with or without coatings. A novel solid freeform fabrication (SFF) method, termed as the slurry mixing and dispensing (SMD) process for making functionally graded materials (FGMs), has been developed to fabricate such a new family of orthopedic implants. The green orthopedic implants produced from the SMD process will be converted to solid implants using a novel sintering method developed recently in our laboratory. This novel sintering method uses HA nano-rods as the starting powder, and leads to dense HA bodies at sintering temperatures as low as 8500C, which is the lowest temperature ever reported in the literature. We have chosen hip implants as the vehicle to study and demonstrate this new family of orthopedic biomaterials because hip fracture is by far the most devastating type of broken bone and it accounts for about 300,000 hospitalizations every year in U.S. To achieve the research goals, five technical tasks have been identified, and a research team with all of the requisite expertise has been formed. We firmly believe that the synergism of this research team will allow us to successfully conduct this multidisciplinary project and push the frontier of the field of orthopedic biomaterials.Broader Impacts: If successful, this project will have favorable social and economical impacts on society because many patients will benefit from this novel technology. The quality of patient life could be improved greatly. Moreover, a reduction in the need for revision surgery could translate into reduced health care costs. Additionally, the SMD process developed in this study can be applied in the future to fabricate other orthopedic implants (e.g., spinal fixation devices, maxillofacial implants, bone graft materials to fill tumor defects, etc.) and many other FGMs for a wide range of applications such as gradient-index lenses, graded armor materials, bipolar plates for fuel cells, and advanced nanocomposites for aerospace, automobile and tool industries. The broad impacts of this program will also be evident in our strong commitment to education, human resource development and outreach, which will have direct impacts on undergraduate students, graduate students, and middle/high school students. We will work with the Connecticut Pre- Engineering Program (CPEP) to increase the number of underrepresented minorities in engineering, science, and technology. We will host CPEP students during summer to provide the students with hands-on labs related to SMD fabrication and orthopedic implants. Mini-projects will be developed so that CPEP students can conduct these mini-projects in one week with the help from graduate students and PIs. Through this new initiative, we will nurture underrepresented minorities towards positive thinking, increase their interest in science and technology, and motivate them to pursue higher education and become future leaders of the society.