Indirect Inactivation of Candida guilliermondii by Using a Plasma Synthetic Jet Actuator: Effect of Advected Charged Particles

Plasma synthetic jet actuators (PSJAs) demonstrated their ability to produce a tubular flow normal to the surface where the dielectric barrier discharge (DBD) is ignited. These fluid dynamics actuators enhance the delivery of reactive and charged species toward the target to be treated. In this work, the efficacy of an octagonal PSJA used to indirectly treat Candida guilliermondii, both in agar substrate and in saline solution, was experimentally studied. The inactivation effect of free charges advected by the induced flow has been investigated as well by interposing a metallic mesh between the actuator surface and the treated sample. Therefore, the passage of charges and their migration toward the sample can either be allowed or prevented simply by having the mesh floating or connected to the ground, respectively. A 4 log and a 2 log colony-forming unit (CFU) reduction were observed for agar substrate and saline solution, respectively, at the highest energy dose treatment with the grid grounded. Under the same conditions but with the grid at floating potential, the presence of advected charges gives an additional 1 log CFU. In addition to biological tests, chemical analyses have been carried out to identify the most important modifications produced by the induced flow into treated water. Results presented in this work demonstrate the efficacy of PSJAs in indirect treatment of C. guilliermondii, both on agar substrate and saline solution, and the inactivation properties of free charges advected by this type of fluid dynamics actuator.