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° 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/C₄F₈plasma 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.