Studies on the use of the coaxial plasma bulb for enhanced wettability of aluminum and polymethylmethacrylate surfaces

• The coaxial plasma bulb is found effective for modifying Al and PMMA surfaces.
• Wettability of the surfaces was optimized by varying plasma discharge parameters.
• Wettability of Al was enhanced by 93.8% and PMMA by 76.2%.
• Plasma treatment increased surface roughness and generated O2-containing groups.

The use of a short coaxial plasma line termed the “plasma bulb” has been investigated for enhancement of the wettability of aluminum (Al) and polymethylmethacrylate (PMMA) surfaces. In comparison with other plasma lines, the plasma bulb uses a single magnetron for microwave generation that could produce plasma for surface treatment. For the treatments of Al and PMMA surfaces, various plasma parameters including gas filling pressure, microwave power and treatment time were investigated for different working gases: argon, oxygen and air. Based from contact angle measurements, the largest increase in the wettability of Al (93.8%) and PMMA (76.2%) samples were obtained using air plasma for 5 min and 10 min treatment time, respectively. AFM and EDX results reveal that increased root-mean-square roughness and possible generation of oxygen-containing groups on the surface are the dominant factors contributing to the enhanced wettability.