Efficient Generation of Plasma‐Activated Aerosols with High Concentrations of Reactive Species Via Silicon Dioxide Coated Surface Acoustic Wave Devices

An effective method to deliver plasma-activated water onto contaminated surfaces is with a surface acoustic wave (SAW) nebulizer that can efficiently produce plasma-activated aerosols. While higher reactive species concentrations in the plasma-activated aerosols promote more efficient bacterial inactivation and hence reduce the amount of aerosols needed to completely eradicate the bacteria colonies, higher concentrations of reactive species themselves are found to lead to lower nebulization rates due to the increased electrical conductivity of the solution. To circumvent this problem, it is shown that coating the SAW substrate with a thin insulating layer of silicon dioxide (SiO2) can significantly mitigate the nebulization rate reduction. Specifically, when the electrical conductivity increases from 0.25 to 4.0 mS cm-1, the 62% drop in the nebulization rate is observed with the uncoated SAW devices is substantially reduced to 19% simply with the SiO2 coating. This can be attributed to the synergistic effects of increased wettability and the suppression of the electrical body force acting on the liquid film. The concomitant increase in the bacterial colony reduction from 17% to 76% demonstrates this solution to be a facile yet effective way of enhancing the efficiency for spray-based bacterial inactivation on contaminated surfaces. Plasma-activated aerosols with high reactive species concentrations can be produced efficiently with the use of silicon dioxide coated SAW nebulization devices. These devices can generate plasma-activated aerosols with electrical conductivities up to 4 mS cm-1 and with substantially lower penalties in the nebulization rate reduction. image