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Rotating Magnetic Field Generator for Biomimetic Freeze-Casting

Project Objective:

Bio-mimicry is a new field in mechanical engineering, nanoengineering, and materials science with great potential to develop multifunctional, high-performance materials and devices inspired by nature. Many natural biological materials, such as bone, abalone shell, porcupine quill and elk antler are lightweight composites that exhibit exceptional mechanical properties tailored to specific functions. The unique properties found in these materials are due to complex architectural features found on multiple length scales, from nano- to macro- levels. With a goal to develop new materials that mimic the structure and match the mechanical properties of various biological materials, MSE graduate students at UCSD have built a freeze casting apparatus to fabricate ceramic scaffolds with highly-ordered, porous microstructures. Freeze casting is a physical process in which an aqueous slurry, typically composed of a solid phase and liquid phase, is directionally frozen, then sublimated to remove the frozen liquid phase and then sintered at high temperatures to densify the porous ceramics. During the freezing process, ceramic particles are pushed between and trapped within the growing ice crystals leading to well-ordered micro-structures. Intricate microstructural features may be controlled by altering the slurry properties or changing the freezing direction and solidification kinetics. To further control the microstructural features of freeze-casting ceramics, new additions to conventional freeze-casting techniques are of great interest, such as applying magnetism during the freezing process. By creating an external rotating magnetic field, UCSD researchers plan to use this to align magnetic particles or create concentration gradients within a slurry during the freeze-casting process. With our Magnetic Field Generator researchers can now use magnetic fields of up to .2 Tesla to mimic the spiraling biological structure of a narwhal tusk. To accomplish this, our team created a large iron horseshoe magnet with one large high power permanent magnet. This magnet is mounted to a stepper motor which rotates the entire magnet about the z- axis. The freeze-cast mold is placed in the open gap of the horseshoe magnet where it can be manipulated by the magnetic field of the magnet. So far, we have had Successful Test creating samples with this spiraling effect.