Manufacturing of Engineered Materials with User-Specified Microstructures using Freeze Casting and Ultrasound Directed Self-Assembly

轻质和坚固的结构是许多工程应用所需要的，例如航空航天复合材料、生物医学植入物和先进机器人。用于创建这些结构的现有技术通常限于特定类型的材料（例如用于熔融沉积成型的聚合物），因此不能适用于可能需要不同材料特性的所有应用。该奖项支持冷冻铸造的基础研究，冷冻铸造使用生长的冰晶来创建多孔结构，超声波引导自组装使用压力波来对齐和加强结构。这种组合工艺将与陶瓷（TiO 2，Al 2 O3和ZrO 2），聚合物（壳聚糖）和金属（Ti）材料一起使用，以创建轻质和坚固的结构。具体来说，将进行实验，展示所涉及的基础科学，包括过程的概念验证，材料特性的仔细测量，通过该过程创建的结构的统计变异性的测量，以及使用该过程的能力，使强大的结构出使用生物启发的微观结构的二氧化钛陶瓷。这项工作的结果将是一种新的制造工艺，可用于用陶瓷、金属和聚合物制造轻质和坚固的结构。一旦得到证实，该项目就可直接应用于生物医学植入物、机器人用高强度低密度结构复合材料和水过滤系统等。该奖项将培养三名研究生和众多本科生研究人员，他们将获得宝贵的经验，并有机会发表和展示他们的研究。该奖项还将资助一个关于先进材料制造和生物灵感设计的互动模块，作为高中女生夏令营的一部分，旨在增加妇女和少数民族对工程的参与。在这个奖项完成后，这个模块将被转换成一个独立的车间，将提供给K-12教师把这些概念带到他们的教室。这项研究的目标是进行基础研究的一个新的制造过程，结合冷冻铸造和超声引导自组装，以及由此产生的多孔，工程材料的机械性能制造使用这个过程。为了演示这一过程，将建立一个新的实验装置，允许冷冻铸造和超声引导自组装，以同时控制工程材料的制造。将进行实验，通过测试浓度为10至20体积%的陶瓷（TiO 2、Al 2 O 3和ZrO 2）、聚合物（壳聚糖）和金属（Ti）组成材料来证明该工艺和0.2至20微米的颗粒尺寸。将研究这些材料的样本间统计变异性。最后，将通过在0.5至10 MHz之间改变超声引导的自组装频率来制造生物启发的微结构，最初使用TiO 2作为材料。在所有情况下，将使用SEM和微型计算机断层扫描（micro-CT）对材料的定制程度进行结构成像和分析，并进行压缩机械测试。

Lightweight and strong structures are needed for many engineering applications such as aerospace composites, biomedical implants, and advanced robotics. Existing techniques for creating these structures are often limited to specific types of materials (such as polymers for fused deposition modeling), and therefore cannot work for all applications where different material properties might be necessary. This award supports fundamental research into the combination of freeze casting, which uses growing ice crystals to create porous structures, and ultrasound directed self-assembly, which uses pressure waves to align and strengthen structures. This combined process will be used with ceramic (TiO2, Al2O3, and ZrO2), polymer (chitosan), and metal (Ti) materials to create lightweight and strong structures. Specifically, experiments will be conducted that demonstrate the basic science involved, including a proof-of-concept of the process, careful measurement of material properties, a measure of the statistical variability of the structures created by this process, and the ability to use this process to make strong structures out of TiO2 ceramics that use bio-inspired microstructures. The results of this work will be a new manufacturing process that can be used to create lightweight and strong structures out of ceramics, metals, and polymers. Once demonstrated, the project has direct applicability to biomedical implants, high strength-low density structural composite materials for robotics, and water filtration systems, among many others. This award will train three graduate students and numerous undergraduate students researchers who will gain valuable experience and have the opportunity to publish and present their research. This award will also fund an interactive module on advanced material fabrication and bioinspired design as part of a summer camp for high school girls aimed at increasing the participation of women and minorities in engineering. At the completion of this award, this module will be converted into a self-contained workshop that will be available for K-12 teachers to bring these concepts to their classrooms.The objective of this research is to conduct basic research on a new manufacturing process that combines freeze casting and ultrasound directed self-assembly, and the mechanical properties of the resulting porous, engineered materials fabricated using this process. To demonstrate the process, a new experimental setup will be built that allows for freeze casting and ultrasound directed self-assembly to simultaneously control the fabrication of an engineered material. Experiments will be carried out that demonstrate the process by testing ceramic (TiO2, Al2O3, and ZrO2), polymeric (chitosan), and metallic (Ti) constituent materials at concentrations of 10 to 20 vol.% and particle sizes of 0.2 to 20 micrometers. The specimen-to-specimen statistical variability of these materials will be investigated. Finally, bio-inspired microstructures will be manufactured by varying the ultrasound directed self-assembly frequency between 0.5 to 10 MHz, initially using TiO2 as the material. In all cases, the extent to which the materials have been tailored will be structurally imaged and analyzed using SEM and micro-computed tomography (micro-CT), and mechanically tested in compression.