RÉSUMÉ

A plasma needle is a novel design of a plasma source at atmospheric pressure to achieve a nonthermal plasma jet. The advantage of the plasma needle is that it can be operated in open air, outside a vessel. The amount of plasma that is generated by a plasma needle is small (∼1 mm), and the plasma is nonthermal. Temperature of the neutral particles and ions is approximately at room temperature, and the particles can suitably interact with living biological cells without damaging the cells. In this work, we report on electrical characteristics and optical emission spectra (OES) of a plasma jet, produced by a direct-current plasma needle that easily interacts with living cells (a human finger). Argon gas is used to run the needle, and the plasmajet is operated on a water-covered agar-gel surface instead of the human finger for stability during characterization. The electrical diagnostics of the plasma needle show that the discharge pulsates. Increased applied voltage increases discharge frequency without affecting discharge voltage or discharge current. The frequency of the discharge is found to increase almost linearly with increasing applied voltage. Using a Boltzmann's plot method from the data collected with OES, we found the estimated excitation temperature was almost independent of the applied voltage.