High-efficiency and low-damage modification of engineering metal materials by oxygen-mixing atmospheric pressure cold plasma jets.

[Display omitted] • A new type of oxygen mixing cold plasma jet is developed to modify metal materials. • The plasma jet can treat various metal materials to be superhydrophilic within 20 s. • The high-efficiency plasma treatment does not cause serious structural damages. • Mechanisms leading to the high-efficiency treatment are systematically studied. Engineering metal materials have been widely developed and applied in aviation, aerospace and biomedicine fields. Wettability improvement of these materials can alleviate problems caused by low adhesion and poor bioactivity, thereby facilitating their practical applications. Compared with other methods, atmospheric pressure cold plasma treatment has better versatility and can efficiently improve wettability without causing serious damages, and has therefore been widely used in polymer hydrophilization. However, when treating metal materials, the cold plasma may induce surface breakdown or have low efficiency. In this paper, we developed a new cold plasma jet by mixing oxygen into working gas to achieve high-efficiency and low-damage modification. When oxygen mixing ratio was 0.4 %, the cold plasma jet could modify TC4 titanium alloy surface to be superhydrophilic within 20 s, which was much more efficient than traditional plasma jet (120 s). We then further investigated the mechanism contributing to higher efficiency, and found that the oxygen-mixing plasma jet did not cause serious damages, while generating more polar groups by higher-concentration active particles, as confirmed by surface energy calculation and optical emission spectra. Besides titanium alloy, the oxygen-mixing plasma jet could also achieve rapid hydrophilization of various engineering metal materials, showing promising application prospects. [ABSTRACT FROM AUTHOR]