Ultrahydrophobic Surface Formation on Materials by Plasma Improvement.

Abstract

Ultrahydrophobic surface formation on materials without changes with the passage of time by plasma improvement has been successfully achieved. The contact angle with water became approximately 160°. It is very important and useful to form the ultrahydrophobic surface such as the lotus surface because it is used in various fields. We used polytetrafluoroethylene (PTFE), polymonochlorotrifluoroethylene (PCTFE), and perfluoroalkoxy (PFA) as materials and treated them by CF4 plasma or CHF3 plasma. In order to investigate the effects of the ions and the radicals in the plasma, the treatment apparatuses of two types were used. One (apparatus I) was the type of parallel plate electrodes and the other (apparatus II) was the induction type. The estimation of material surface characteristics was carried out by measurements of the contact angle of the material surface with water, the weight of the materials and SEM observation. In case the materials were placed on the power electrode in the apparatus I and the input power for the improvement was large, ultrahydrophobic surfaces without change with time were produced. In case of PFA, such surfaces were formed even if it was put on the earth electrode. Such surfaces were not made by using the apparatus II. It was found that the formation of ultrahydrophobic surfaces without change with time could be attained by the following methods. (1) Plasma that has fluoric ions and fluoric radicals as its composition elements should be used. (2) Sheath voltage between the plasma and the material should be large (high). The roughness on the surface and the stable bond between fluoric atoms and atoms of the material on the surface should be formed. (3) Material whose structure is suitable for becoming ultrahydrophobic should be used.