Optical Emission Spectroscopy and Contact Angle Study of Plasma Cleaning of Titanium Alloy Surfaces: Argon Plasma

Abstract

Plasma cleaning is common in the preparation of titanium medical devices. In this study, we examine the use of continuous in situ measurements with optical emission spectroscopy (OES) during plasma cleaning and wet contact angle as a tool to assess titanium implant cleanliness. Plasma cleaning was performed in argon plasma at 66.7 Pa in a commercially available radio-frequency (RF) power plasma system using 25 or 100 W of power. During cleaning, the intensities of OES lines at 386 and 418 nm, as related to surface contaminants, decreased over time and reached a baseline level in ~1 h. However, the water contact angle (WCA) decreased more rapidly, reaching ≤10 degrees in 3-5 sec and further decreased to the limit of detection of ~1 ± 1 degree in 20 min using 25 W plasma and in 1 min using 100 W plasma. The OES data indicate that plasma cleaning starts with rapid removal of contaminants from pronounced regions that are better exposed to the plasma and is followed by prolonged cleaning related to the removal of contaminants from less accessible regions. The delayed rise in WCA demonstrates a limitation in using that technique to assess cleanliness and shows how OES is a useful tool to better understand and control plasma cleaning of titanium surfaces.

Synergistic Effect of Cold Plasma Treatment and RGD Peptide Coating on Cell Proliferation over Titanium Surfaces

“…Plasma is as an established method for the cleaning of titanium materials to be used medically [49]. Also, plasma treatment increases surface hydrophilicity via affecting oxide layer which interacts with proteins that play role on cell attachment [28,50,51].…”

Effects of discharge mode and gas composition for plasma‐hydrophilized titanium surface on hydrophilic sustainability

“…[12][13][14] Despite these advantages, however, hydrophilization of Ti-based materials through plasma treatment is hardly used in industry because the obtained hydrophilic surface gradually converts to a hydrophobic surface with time. 15,16 Att et al reported that the hydrophilicity of Ti surfaces deteriorated when stored in air owing to the re-adsorption of contaminant hydrocarbons. 17 Therefore, to apply the plasma treatment of Ti-based materials as a surface hydrophilization process practically, the technology for modifying "non-deteriorated hydrophilic surfaces" is required.…”

“…Despite these advantages, however, hydrophilization of Ti‐based materials through plasma treatment is hardly used in industry because the obtained hydrophilic surface gradually converts to a hydrophobic surface with time 15,16 . Att et al reported that the hydrophilicity of Ti surfaces deteriorated when stored in air owing to the re‐adsorption of contaminant hydrocarbons 17 .…”