In this paper, a plasma-induced hemi-wicking phenomenon observed on hydrophobic sanded polymer surfaces, polypropylene (PP), polyethylene terephthalate (PET) and polyethylene (PE) is reported. An atmospheric-pressure argon plasma jet was used to treat a limited area of the carefully sanded polymer surfaces to induce the hemi-wicking phenomenon. Such hemi-wicking triggered by the plasma activation is different from the traditional type, which is achieved purely by the surface topography. Surface analyses by X-ray photoelectron spectroscopy (XPS) and water contact analysis (WCA) show that the combination of sanding and plasma treatment increased the oxygen-to-carbon ratio, which is highly beneficial for surface hydrophilicity. The shear stress tests show that the combination of sanding and plasma treatment can enhance the shear stress by 125%, 95%, and 296% on PP, PET, and PE, respectively. The study shows that the newly developed technique by combining the sanding and plasma processing for polymers could be a potentially useful method in future industry applications.

The discharge of atmospheric-pressure plasma jet (APPJ) applied on the water was studied by varying an air gap between a powered electrode and the water, and the alternating current power. It was found that the streamers were converged by the air flow to form a streamer bridge to allow current flow across the air gap to transition from a dielectric barrier discharge (DBD) mode to a streamer mode. Because the AC power alternates periodically, this study proposed an analysis without the parameter of time by the voltage amplitude to power characteristic. It was found that the longer distance required higher voltage amplitude and power to transition. Prior research of plasma rarely mentioned the real power and the reactive power, which are essential for electric devices. Because different discharge mode produces different species, this study proposed a simple method to analyze and predict discharge modes based on the power factor, which presents the relationship of the real power and the reactive power. It was found that the streamer mode had a higher power factor than the DBD mode, and thus the power factor decides the discharge mode. Therefore, a power factor analysis can be a systematic basis to produce the required discharge by changing the equivalent capacitance and resistance to change the reactive power and real power. This study proposed a simple method to analyze periodic discharge by the intensified charge-coupled device (ICCD). A period of the AC was divided into twelve timings. For each timing, each shot was configured to have the minimum exposure time to avoid the afterimage. Thousands of shots were overlapped into one snapshot to increase the fluorescence and make such snapshot more representative for the timing. Snapshots show that the streamer bridge was only formed in specific timings periodically.