Superhydrophobic treatment using atmospheric-pressure He/C4F8 plasma for buoyancy improvement

A superhydrophobic miniature boat was fabricated with aluminum alloy plates treated with atmospheric-pressure helium (He)/octafluorocyclobutane (C4F8) plasma using 13.56MHz rf power. When only 0.13% C4F8 was added to He gas, the contact angle of the surface increased to 140 degrees and the surface showed superhydrophobic properties. On the basis of chemical and morphological analyses, fluorinated functional groups (CF, CF2, and CF3) and nano-/micro-sized particles were detected on the Al surface. These features brought about superhydrophobicity similar to the lotus effect. While the miniature boat, assembled with plasma-treated plates, was immersed in water, a layer of air (i.e., a plastron) surrounded the superhydrophobic surfaces. This effect contributed to the development of a 4.7% increase in buoyancy. In addition, the superhydrophobic properties lasted for two months under the submerged condition. These results demonstrate that treatment with atmospheric-pressure He/C4F8 plasma is a promising method of improving the load capacity and antifouling properties, and reducing the friction of marine ships through a fast and low-cost superhydrophobic treatment process. (C) 2015 The Japan Society of Applied Physics