Idalia Ramirez1, Aaron Cipriano1,2, Huinan Liu1,2

1Department of Bioengineering, 2Materials Science & Engineering Program

Motivation Results: Current–Transient and Surface Topography

Background: Mg-based biomaterials and anodization Results: PDP Measurements and Tafel Analysis

Materials and Methods Acknowledgements & References

[1] Aaron F. Cipriano, et al. “Anodic Growth and Biomedical Applications of TiO2 Nanotubes”. Journal of Biomedical Nanotechnology 10 (2977-20014). [2] Mark P. Staiger, et al “Magnesium and its alloys as orthopedic biomaterials: A review”, Biomaterials 27 (2006): 1728-1734[3] Miller C, et.al. Undergraduate Research Journal 2012 (6) 33- 37

The results of this poster are product of MacREU R’side. The Materials Connection Riverside is a Research Experience for Undergraduate students site sponsored by the National Science Foundation Division of Materials Research under grant DMR-1359136. Additional support from [XXX]

MacREU R’side ‘15

References Acknowledgement

Magnesium anodization for biodegradable implants: Nano-scale surface topography and corrosion resistance

Magnesium (Mg) has attracted much attention in the past decade for its potential biomedical applications. The mechanical and biological properties of Mg make it an ideal candidate as a material to be used in biodegradable implants. In order to accomplish that goal, the rapid corrosion of Mg must be addressed in order to give the bone enough time to heal and meet clinical requirements.

Our goal is to engineer a solution that addresses the rapid corrosion of Mg to maximize its potential for biomedical implant applications.

Benefits

Generates nanoscale topography1

Topography controls cell behavior1

Improves corrosion resistance

Enhance implant durability to meet clinical needs

Biological Properties4th Most abundant cation in human body

Human body can metabolize excess Mg

Mg degradation products are osteo-conductive

Mg is very anodic, therefore corrodes easily

Figure 3: (a) PDP curves of anodized samples measured in SBF at 37 C and photos of samples after PDP measurements, and corresponding corrosion (b) potential and (c) current density of anodized samples obtained from Tafel-type extrapolation.

Results showed that the anodic behavior of anodized and annealed samples do change in comparison to pure Mg, but did not confirm that the corrosion rate is improved. Optical images showed distinct corrosion behavior after PDP tests. The samples anodized at 1.9 V vs Ag/AgCl showed a slight improvement in corrosion current density (i.e. corrosion rate) and will studied using immersion tests to investigate the long-term corrosion behavior.

Mechanical Properties

Cortical Bone

Magnesium[Mg]

Titanium[Ti]

Density (g/cm3)

1.8-2.1 1.74-2.0 4.4-4.5

Elastic Modulus (GPa)

3-20 41-45 110-117

Compressive yield strength (MPa)

130-180 65-100 758-1117

What: Versatile and inexpensive electrochemical process to induce oxidation on metalsHow: In the electrochemical circuit, the working electrode (i.e. Mg) is the anode and induces oxidationWhy: To increase corrosion resistance

Figure 2: (a-c) SEM images of Mg samples after anodization at different potentials (left to right) and different magnification (top to bottom). (d-e) Surface elemental composition at different potentials and color coordinated with present element.

Figure 1: (a) Current-transient curves of anodized Mg samples in 10M KOH electrolyte and photos of samples after anodization.

I. Embed Mg (99.95%, Alfa Aesar)

II. Grind with sandpaper (240-1200 grit)III. Polish & Clean (Diamond

paste 9-1/4 micron, sonicate with ethanol/acetone)

Initial sample preparation1

2 Anodization

I. Cut out samplesII. Anneal (450o C for 6 hours)III. Surface characterization

(SEM/EDS of surface and cross-section)

3 Intermediate sample preparation

I. Re-embed samples with custom compression mold

Re-embed Sample4

I. Collect data PDPII. Tafel AnalysisIII. Surface

characterization (SEM/EDS)

5 In-vitro corrosion

Results showed homogenous but distinct nano-scale surface topographies in as little as 100 mV intervals between 1.9 V and 2.0 V. Samples anodized at 1.9 V showed the most ideal O/Mg ratio by surface elemental composition. The surface characteristics at potentials 1.8, 1.9 and 2.0 V were further analyzed through SEM.

I. Electrolyte: 10 M KOH in DI water (38 mL plus stir bar)

II. Potential: 1.8-2.0V vs. Ag/AgCl

III. Duration: 2 hours (At room temp)

IV. Collect I(t)

(c)