DEVELOPMENT OF AN IMPLANTABLE CHIP FOR IN-VIVO CORROSION RATE MONITORING
Open Access
- Author:
- Hartsock, Anna
- Graduate Program:
- Engineering Science
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- April 20, 2012
- Committee Members:
- Barbara Shaw, Thesis Advisor/Co-Advisor
Mark William Horn, Thesis Advisor/Co-Advisor
Elzbieta Sikora, Thesis Advisor/Co-Advisor - Keywords:
- Corrosion monitoring
magnesium
titanium
in vitro - Abstract:
- Bio-absorbable medical devices are becoming more popular for temporary implants. Bone plates and cardiovascular stents are the biomedical devices that, in some cases, can be classified as temporary devices. Magnesium alloys are currently under investigation for these products due to their biocompatible mechanical properties. Among metals, pure magnesium (Mg) corrodes readily. Therefore, magnesium alloys are needed to alter the rate of corrosion to ensure a device would be present throughout tissue healing. The primary goal of this thesis research was to test a three-electrode planar device that was developed for corrosion monitoring under in-vivo conditions. The device was produced using micro-electronic lithographic patterning. This device was designed to eventually be used to test candidate bioabsorbable magnesium-titanium (Mg-Ti) alloys produced via evaporation. Prior to in-vivo testing, devices were tested under in-vitro conditions (outside the body in a simulated environment). A corrosion resistant material (sputtered Ti) was used for initial testing, while sputtered platinum (Pt) was used for both the counter and quasi-reference electrodes. Through open circuit potential monitoring and corrosion rate determination, it was concluded that the device was able to provide reliable data. An average corrosion rate of 0.005 ± 0.008 mm/year was found for the sputtered Ti. This value is comparable to those found in literature. A secondary goal of this thesis was to evaluate the corrosion rates of candidate Mg-Ti alloys for possible use as implant materials. The most promising of these will eventually be used in the three-electrode device in the future. The candidate alloys were produced via physical vapor evaporation. Alloys with varying amount of Ti were investigated using electrochemical corrosion techniques. A Mg-Ti composition of 2 wt.% Ti would be the most ideal for these biomedical applications. A corrosion rate of 3.38 mm/year was determined and would allow for significant healing time.