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

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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.