Deposition of stable hydrophobic coatings with in-line CH4 atmospheric rf plasma

A CH4 atmospheric rf plasma treatment process was demonstrated for hydrophobic treatments of various substrates including metallic and insulating surfaces as well as flat and rough surfaces. A stable rf glow plasma was generated over a 1 cm x 16 cm area using a cylindrical electrode geometry. A typical hydrophobic treatment speed was 5-10 cm min(-1). CH4 plasma polymerization deposited a very smooth hydrocarbon layer composed of CH2 and CH3 groups. The inclusion of oxygenated species was less than 1%. On flat substrates, the water contact angle was similar to 90 degrees. On rough surfaces such as cotton, the contact angle reached up to 150 degrees. Since this method does not require vacuum or any special venting systems, it will be suitable for in-line processing of a wide range of substrate materials.