Date of Award

2011

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

First Advisor

Sankar, Jagannathan Dr.

Abstract

Magnesium (Mg) and its alloys are great candidates for uses in orthopedic implant applications due to their biocompatibility, mechanical properties and degradability. However, Mg and its alloys are susceptible to accelerated degradation rates due to galvanic corrosion, which leads to unpredictable corrosion behavior. The objective of this study is to develop biocompatible, functional thin film magnesium oxide (MgO) coatings that: (1) serve as a galvanic separator between metallic substrates and metallic coatings, (2) control the rate of corrosion of Mg-based implants, (3) have controlled resorption times based on coating thickness, (4) promote osseointegration and (5) are predictable in corrosive environments. An Mg screw was coated with copper (Cu) using direct current (DC) magnetron sputtering and galvanic corrosion was observed from the direct contact of the metallic substrate and metallic coating. MgO thin films were developed, to serve as an intermediate layer, using pulsed DC reactive magnetron sputtering. The sputtering of MgO was optimized through oxygen content, frequency and power. Multilayered MgMgO-Cu and Mg-MgO systems were created and individual layer thicknesses were measured using X-ray reflectometry (XRR) analysis software. Immersion tests were performed on Mg-MgO systems with varying thicknesses using the optical density xvii method. The tests were performed at room temperature with deionized water and phosphate buffered saline (PBS) and were also done at 37ºC with albumin, media, media with fetal bovine serum (FBS), saline and PBS. The results were used to calculate resorption times and this information was used to perform a cell adhesion assay. This study shows that MgO exhibited biocompatibility, controlled the rate of Mg corrosion and is a good candidate for a galvanic separator material.

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