Low temperature, atmospheric pressure, direct current microplasma jet operated in air, nitrogen and oxygen

Micro-plasma jets in atmospheric pressure molecular gases (nitrogen, oxygen, air) were generated by blowing these gases through direct current microhollow cathode discharges (MHCDs). The tapered discharge channel, drilled through two 100 to 200 mu m thick molybdenum electrodes separated by a 200 mu m thick alumina layer, is 150 to 450 mu m in diameter in the cathode and has an opening of 100 to 300 mu m in diameter in the anode. Sustaining voltages are 400 to 600 V, the maximum current is 25 mA. The gas temperature of the microplasma inside the microhollow cathode varies between similar to 2000 K and similar to 1000 K depending on current, gas, and flow rate. Outside the discharge channel the temperature in the jet can be reduced by manipulating the discharge current and the gas flow to achieve values close to room temperature. This cold microplasma jet can be used for surface treatment of heat sensitive substances, and for sterilization of contaminated areas.