Uniform Area Treatment for Surface Modification by Simple Atmospheric Pressure Plasma Treatment Technique

The atmospheric pressure plasma jet (APPJ) has a merit to treat curved or 3D surface without using a ground electrode but nonetheless limits applications for expanding treatment area due to the localized ionization energy induced by the propagation along the direction of guided ionization waves. This paper proposes a uniform area treatment for surface modification based on the experimental case studies relative to variations of the APPJ structures, such as the number of array jets and guide-tube, including bluff-body (GB) system plus gas compositions. In these case studies, the current, infrared (IR), and optical emission spectrum (OES) are analyzed to investigate the factors affecting intensive glow-like plasma generation for uniform area treatment. Plasma-treated polyethylene terephtalate (PET) films are additionally examined to check the possibility of uniform area treatment for surface modification by using atomic force microscope (AFM), Fourier transform-infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and water contact angle (WCA). Only in case of three-array jets with GB system using Ar with O2 gas, the intense glow-like plasma is observed to be produced widely in discharge space, thereby enabling the entire surface of PET films to be treated uniformly. In particular, the proposed APPJs are observed to generate more abundantly the reactive nitrogen species (RNS) ranging from 330 and 380 nm and the reactive oxygen species (ROS) at 777.4 and 844.6 nm. Furthermore, the plasma-treated PET film shows that the abundant RNS and ROS play a significant role in smoothening and changing its surface into hydrophilic surface. As a result, it is confirmed that the intense glow-like plasma generated broadly by the proposed APPJs can uniformly treat the entire surface of PET films.