A needle-rectangular loop sterilizer with self-ejected plasma by using positive and negative direct-current voltages

We designed a portable direct-current (DC) jet sterilizer that discharges self-excited plasma through a needle-rectangular loop sterilizer. The device is sized ∅ 30 mm × 40 mm. The tungsten needle is connected to the high voltage source and to the copper rectangular loop with earthing wire. Under high-voltage DC (±9.6 kV) at atmospheric pressure, the plasma jets killed Escherichia coli and Staphylococcus aureus in the absence of an externally connected carrier gas. Under the same conditions, the E. coli and S. aureus were destroyed after 90 s and 120 s respectively by the positive plasma jet, and after 120 s and 150 s respectively by the negative plasma jet. Thus, the sterilization efficiency of the positive plasma jet exceeds that of the negative plasma jet.