Effects of the ground-electrode temperature on the plasma physicochemical processes and biological inactivation functions involved in surface dielectric barrier discharge

Abstract

In this work, a surface dielectric barrier discharge (SDBD) device coupled with power electronics technology was designed for precise control of the ground-electrode temperature to investigate the dynamic behavior of the physicochemical processes and biological inactivation functions involved in SDBD plasma. It was found that an increase of the electrode temperature from 30 to 210 °C reduced the breakdown voltage and increased the current pulse amplitude because the reduced electric field strength and average electron density of the SDBD plasma were consistently enhanced. The change in the plasma-chemistry mode (O3-dominant to NO x -dominant) was more sensitive to the ground-electrode temperature than that of the power density and gas temperature. O3 in the gas and liquid phases could not be detected at electrode temperatures above 90 °C, and the NO x mode almost immediately occurred after the plasma was turned on for ground-electrode temperatures of ⩾180 °C. The increase in the electrode temperature increased the acidity of the plasma-activated water and, more importantly, short-lived reactive species OH and NO were detected at electrode temperatures ⩾120 °C in the case of aqueous solutions treated directly with SDBD plasma. The biological inactivation function of the SDBD plasma, i.e. for bacterial suspensions and tumor cell cultures, was improved by about three orders of magnitude and 40% at the optimal electrode temperatures of 180 °C and 120 °C, respectively. This is an important breakthrough for development of SDBD-based biomedical devices for specific purposes on a commercial level by regulating the plasma chemistry through the ground-electrode temperature, overcoming the limitations of chamber heating and compressed air supply.