A system is disclosed which comprises a power supply； and a plasma-generating device comprising a tip having an outlet with a diameter in a range of 0.3-0.8 mm, the plasma-generating device configured for generating and discharging through the outlet a plasma flow, wherein the power supply is configured to deliver a controlled pattern of current to the plasma flow via the plasma-generating device, the controlled pattern of current alternating between a low current level in a range of 3-10A, and a high current level in a range of 25-30A.
