A Novel DC-Driven Atmospheric-Pressure Cold Microplasma Source for Biomedical Application

The application of atmospheric-pressure cold plasmas in biomedicine has attracted intense interests in the past two decades. In this paper, a novel atmospheric-pressure dc microplasma source is presented. Compared to typical dc discharges, the afterglow generated by this low-power dc discharge is of room-like temperature and reactive plasma chemistry. Argon gas mixed with nitrogen, oxygen, or water vapor are used as the working gases for the selective production of different reactive species. With Ar + N2working gas, metastable N2(A) are generated in the discharge zone and flow along the gas channel forming a plasma plume in the open space. Various reactive oxygen and nitrogen species, including OH, O3, and NO, are able to be produced selectively when Ar mixes with different gas impurities. A room-like gas temperature below 40 °C is achieved for the reactive afterglow through gas flow cooling and low-current operation. The heat deposition from the discharge on treated objects is studied with a glass substrate by thermal infrared imaging. It is observed that the thermal field on the glass plate expands fast with the rise of surface peak temperature, which should be controlled or avoided in specific heat-sensitive material treatments. Bactericidal treatments of Candida albicans are carried out, and distinct inactivation effects are obtained with different working gas mixtures which correspond to various biological contributions of different reactive species in the discharge afterglow.