Hydrophobic coating on glass surfaces via application of silicone oil and activated using a microwave atmospheric plasma jet

• The microwave atmospheric plasma jet was used to fabricate hydrophobic glass.
• A water contact angle of 105.7° was obtained at optimum discharge parameters.
• Enhanced hydrophobicity was attributed to increased roughness and introduced CH2 and CH3 bonds.
• Surface energy of glass after plasma treatment with oil decreased to 27.97 mN/m.
• Hydrophobic property of the plasma-treated glass remains stable after 50 days.

In this study, a hydrophobic coating on glass surfaces was fabricated by application of a silicone oil lubricant and activated using a microwave atmospheric plasma jet. Optimization of the treatment was done by variation of the working gas flow rates, input microwave power and plasma treatment time, based on contact angle measurements. In comparison with the untreated glass (37.6°), results show that at best discharge conditions of 600 W microwave power, 5/0.5 LPM Ar/N2 flow rate and 10 s treatment time, the plasma-treated glass obtained a water contact angle of 105.7°. Surface energy of the glass also decreased from 45.07 mN/m for the untreated to 27.97 mN/m after plasma treatment. Atomic force microscopy (AFM) and Fourier transform infrared (FTIR) spectroscopy results suggest that increased root-mean-square roughness and introduction of hydrophobic species may have been responsible for the hydrophobicity of the glass surface.