In Vitro Biodegradation of a-C:H:SiO_x Films on Ti-6Al-4V Alloy.

Area of Science:

• Materials Science
• Biomaterials Engineering
• Surface Chemistry

Background:

• Titanium alloys (Ti-6Al-4V) are widely used in medical implants.
• Surface coatings are crucial for improving biocompatibility and performance of implants.
• Understanding biodegradation and ion precipitation is vital for long-term implant success.

Purpose of the Study:

• To investigate the in vitro biodegradation of amorphous hydrogenated silicon oxide (a-C:H:SiOx) films of varying thicknesses.
• To evaluate the effect of film thickness on surface morphology, adhesion, and ion precipitation.
• To determine the suitability of these films for medical applications like cardiovascular stents.

Main Methods:

• Plasma-assisted chemical vapor deposition (PACVD) to create a-C:H:SiOx films on Ti-6Al-4V substrates.
• In vitro immersion testing in 0.9% NaCl solution for five weeks.
• Surface analysis using morphometric analysis and Rockwell hardness testing (VDI 3198).
• Elemental composition analysis using energy-dispersive X-ray spectroscopy (EDX).

Main Results:

• Increasing a-C:H:SiOx film thickness (0.5-3 µm) slightly reduced surface roughness.
• Adhesive strength was rated HF1 for 0.5 µm and HF2-HF3 for thicker films, indicating strong adhesion.
• NaCl ion precipitation (Na+, Cl-) was significantly lower on coated surfaces compared to uncoated surfaces.
• Multiple regression equations correlated elemental composition with reduced ion precipitation.

Conclusions:

• a-C:H:SiOx films exhibit strong interfacial adhesion to Ti-6Al-4V substrates.
• Film thickness influences surface properties and significantly reduces salt ion precipitation.
• These films demonstrate potential for use in cardiovascular stents and heart pump components due to good adhesion and low ion precipitation.