Patterned superhydrophobic surface fabrication by coupled atmospheric pressure RF and pulsed volume dielectric barrier discharges

Superhydrophobic (SH) surfaces have great potential in numerous applications. Plasma polymerization is one of the most efficient technologies for engineering SH surfaces due to its unique feature of tailoring surface chemistry and surface topography simultaneously. Herein, a novel sandwich-like plasma device that consists of contiguous two-stage dielectric barrier discharges (DBDs) driven by the time-modulated radiofrequency (RF) and pulsed power sources is proposed to polymerize hexamethyldisilazane (HMDSN) at atmospheric pressure for the purpose of SH surface engineering. The coordination of dual power sources shows effective performances in plasma operation and material surface treatment, compared to the case driven by any power source alone. Easy ignition and enhanced stability are achievable for the upper RF DBD with the assistance of the bottom pulsed DBD. Vice versa, a diffuser pulsed discharge is obtainable with the input of abundant active and energetic species and precursor fragments from the upper RF plasma. Diagnostic measurements by optical emission spectroscopy and Mie scattering demonstrate that HMDSN fragmentation and nanoparticle nucleation are initiated predominantly by the RF-driven plasma. These species and nanoparticles are further fragmented and dispersed in the bottom pulsed discharge. Consequently, the desired SH surface is fabricated with a similar pattern to that of the pulsed DBD geometry. This study provides a new pathway based on the plasma-assisted method to control surface hydrophobicity and provides insights on a new plasma deposition method suitable for atmospheric pressure material processing