Department: Mechanical & Aerospace Engineering
Research Institute Affiliation: Agile - CaliBaja Center for Resilient Materials & Systems
Faculty Advisor(s): Joanna M. McKittrick

Primary Student
Name: Michael Brian Frank
Email: mbfrank@ucsd.edu
Phone: 858-534-5425
Grad Year: 2016

Student Collaborators
Sze Hei Siu, shsiu@ucsd.edu | Jerry Ng, jen002@ucsd.edu | Ali Ismail, alismail@ucsd.edu | Ivan Torres, ivtorres@ucsd.edu | Chin-Hung Liu, chl261@ucsd.edu | Keyur Karandikar, kkarandi@ucsd.edu | Steven Naleway, snaleway@eng.ucsd.edu

Bone has a hard mineral phase and a compliant biopolymer phase within a composite that is both lightweight and strong. Osteoporosis degrades spongy bone preferentially over time and leads to bone brittleness, especially in the elderly. Currently, bone implants made of titanium are often too stiff and can require follow-up surgeries. A porous ceramic material that can mimic spongy bone for a one-time implant is a much better solution for an aging population. Porous scaffolds can be made by freeze casting of ceramic powders and use of an applied magnetic field enables fabrication of a porous scaffold that resembles spongy bone. The freezing of water separates a slurry of magnetized alumina particles into lamellae between growing ice crystals. A weak magnetic field applied at the same time throughout the freezing induces alignment of the lamellae structures. The frozen block is freeze dried to extract the ice and sintered to produce a porous scaffold with aligned pores in both the longitudinal (ice growth direction) and transverse (magnetic field direction) axes. Compression testing of scaffolds in the transverse axis that were subject to an applied magnetic field had two times the stiffness. This result mirrors how spongy bone pores naturally align within the load bearing direction of the ball-and-socket hip joint. Alumina particles surface magnetized with charged ferrofluid are new functional materials that can be used for fabrication of multi-axis strengthened porous structures. Magnetic properties of magnetized materials are compared and the ideal magnetic field strength needed to induce alignment throughout the scaffold center, rather than just at the poles, is determined. This work is supported by funding provided by the Multi-University Research Initiative through the Air Force Office of Scientific Research (AFOSR-FA9550-15-1-0009).

Industry Application Area(s)
Energy/Clean technology | Life Sciences/Medical Devices & Instruments | Materials

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