Stiff, porous scaffolds from magnetized alumina particles aligned by magnetic freeze casting

Michael B Frank; Steven E Naleway; Tsuk Haroush; Chin-Hung Liu; Sze Hei Siu; Jerry Ng; Ivan Torres; Ali Ismail; Keyur Karandikar; Michael M Porter; Olivia A Graeve; Joanna McKittrick

doi:10.1016/j.msec.2017.03.246

Stiff, porous scaffolds from magnetized alumina particles aligned by magnetic freeze casting

Mater Sci Eng C Mater Biol Appl. 2017 Aug 1:77:484-492. doi: 10.1016/j.msec.2017.03.246. Epub 2017 Mar 29.

Authors

Affiliations

¹ Materials Science and Engineering Program, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA. Electronic address: mbfrank@ucsd.edu.
² Department of Mechanical Engineering, University of Utah, 1495 E 100 S, Salt Lake City, UT 84112, USA.
³ Department of Mechanical and Aerospace Engineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.
⁴ Materials Science and Engineering Program, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.
⁵ Department of Mechanical Engineering, Clemson University, Clemson, SC 29634, USA.
⁶ Materials Science and Engineering Program, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA; Department of Mechanical and Aerospace Engineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.

PMID: 28532056
DOI: 10.1016/j.msec.2017.03.246

Abstract

Bone consists of a hard mineral phase and a compliant biopolymer phase resulting in a composite material that is both lightweight and strong. Osteoporosis that degrades spongy bone preferentially over time leads to bone brittleness in the elderly. A porous ceramic material that can mimic spongy bone for a one-time implant provides a potential solution for the future needs of an aging population. Scaffolds made by magnetic freeze casting resemble the aligned porosity of spongy bone. A magnetic field applied throughout freezing induces particle chaining and alignment of lamellae structures between growing ice crystals. After freeze drying to extract the ice and sintering to strengthen the scaffold, cubes from the scaffold center are mechanically compressed along longitudinal (z-axis, ice growth direction) and transverse (y-axis, magnetic field direction) axes. The best alignment of lamellar walls in the scaffold center occurs when applying magnetic freeze casting with the largest particles (350nm) at an intermediate magnetic field strength (75mT), which also agrees with stiffness enhancement results in both z and y-axes. Magnetic moments of different sized magnetized alumina particles help determine the ideal magnetic field strength needed to induce alignment in the scaffold center rather than just at the poles.

Keywords: Ceramic scaffold; Ferrofluid; Freeze casting; Magnetic alignment; Mechanical properties.

MeSH terms

Aluminum Oxide
Ceramics
Freeze Drying
Freezing
Magnetics*
Porosity
Tissue Engineering
Tissue Scaffolds

Substances

Aluminum Oxide