Two Atmospheric Pressure Plasma Jets Driven by Phase-Shifted Voltages: A Method to Control Plasma Properties at the Plasma–Surface Interface

Atmospheric pressure plasma jets have the distinctive ability to project a plasma away from its electrodes, making it an attractive plasma source for a variety of surface treatment applications. Unfortunately, the small effective area of plasma jets inhibits their more widespread use. To remedy this, multiple plasma jets can be used in tandem to enhance their effective area. When used together, the plasma jets will interact and alter one another’s properties. The goal of this work is to understand the interaction between plasma jets and use this interaction to influence their properties at the plasma–surface interface by tailoring the voltage waveforms driving two interacting plasma jets. In this work, two piezoelectric-driven plasma jets are positioned at a 130° angle from one another such that they will intersect on the surface of a substrate. The phase difference between the high-voltage waveforms generating the plasma jets was varied to manipulate the properties of the resultant plasma. It was found that increasing the phase difference between the plasma jets required less total power than when the two jets were operated independently and caused changes to the emission spectrum and an increase in the electron density at their intersection point. As such, changing the phase between two plasma jets can be used to alter the power consumption, the electron density, and the electron kinetics of the plasma at the surface of a substrate, which may be useful for a variety of applications.