Inactivation of SARS CoV-2 on porous and nonporous surfaces by compact portable plasma reactor.

We report the inactivation of SARS CoV-2 and its surrogate-Human coronavirus OC43 (HCoV-OC43), on representative porous (KN95 mask material) and nonporous materials (aluminum and polycarbonate) using a Compact Portable Plasma Reactor (CPPR). The CPPR is a compact (48 cm3), lightweight, portable and scalable device that forms Dielectric Barrier Discharge which generates ozone using surrounding atmosphere as input gas, eliminating the need of source gas tanks. Iterative CPPR exposure time experiments were performed on inoculated material samples in 3 operating volumes. Minimum CPPR exposure times of 5-15 min resulted in 4-5 log reduction of SARS CoV-2 and its surrogate on representative material samples. Ozone concentration and CPPR energy requirements for virus inactivation are documented. Difference in disinfection requirements in porous and non-porous material samples is discussed along with initial scaling studies using the CPPR in 3 operating volumes. The results of this feasibility study, along with existing literature on ozone and CPPR decontamination, show the potential of the CPPR as a powerful technology to reduce fomite transmission of enveloped respiratory virus-induced infectious diseases such as COVID-19. The CPPR can overcome limitations of high temperatures, long exposure times, bulky equipment, and toxic residuals related to conventional decontamination technologies.

Distributed compact plasma reactor decontamination for planetary protection in space missions.

This paper presents a proof-of-concept study establishing effectiveness of the Active Plasma Sterilizer (APS) for decontamination in planetary protection. The APS uses Compact Portable Plasma Reactors (CPPRs) to produce surface dielectric barrier discharge, a type of cold plasma, using ambient air to generate and distribute reactive species like ozone used for decontamination. Decontamination tests were performed with pathogenic bacteria (Escherichia coli and Bacillus subtilis) on materials (Aluminum, Polycarbonate, Kevlar and Orthofabric) relevant to space missions. Results show that the APS can achieve 4 to 5 log reductions of pathogenic bacteria on four selected materials, simultaneously at 11 points within 30 min, using power of 13.2 ± 2.22 W. Spatial decontamination data shows the APS can uniformly sterilize several areas of a contaminated surface within 30 min. Ozone penetration through Kevlar and Orthofabric layers was achieved using the CPPR with no external agent assisting penetration. Preliminary material compatibility tests with SEM analysis of the APS exposed materials showed no significant material damage. Thus, this study shows the potential of the APS as a light-weight sustainable decontamination technology for planetary protection with advantages of uniform spatial decontamination, low processing temperatures, low exposure times, material compatibility and the ability to disinfect porous surfaces.

Inactivation of Pseudomonas aeruginosa and Methicillin-resistant Staphylococcus aureus in an open water system with ozone generated by a compact, atmospheric DBD plasma reactor.

Ozone is a well-known disinfecting agent that is used as an alternative for chlorine in many applications, including water decontamination. However, the utility of ozone in water decontamination is limited by high electrical power consumption and expensive, bulky equipment associated with ozone generation. This study investigates the effectiveness of a lightweight, compact surface dielectric barrier discharge (SDBD) reactor as an ozone generator to inactivate Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus (MRSA) in an open water system. Experimental details are provided for ozone generation technique, mixing method, ozone concentrations in air and water, and input energy required to produce adequate ozone concentrations for bacterial inactivation in a contaminated, open water system. Specifically, an active plasma module (APM) reactor system of size 48 cubic centimeters, weighing 55 grams, with a maximum ozone yield of 68.6 g/KWh was used in atmospheric conditions as the source of ozone along with an air pump and a diffusion stone for mixing the ozone in water. Over 4-log reduction in P. aeruginosa concentration was achieved in 4 minutes with 0.1 mg/L ozone concentration in an open water system using 8.8 ± 1.48 J input energy. Also, over 5-log reduction in MRSA concentration was achieved in 2 minutes with 0.04 mg/L ozone concentration in an open water system using 4.4 ± 0.74 J input energy.

Functional relationship between material property, applied frequency and ozone generation for surface dielectric barrier discharges in atmospheric air.

We report the experimental characterization of ozone generation in dielectric barrier discharges as a function of the material and characteristics of the dielectric barrier, operating frequency and the power consumed by a surface DBD-plasma reactor in air at atmospheric pressure. To identify the effect of the dielectric barrier, ozone production curves corresponding to ten dielectric barriers with different effective thicknesses and thermal properties are compared and analyzed for two combinations of voltage amplitudes and frequencies: 7 kV/10 kHz and 8.5 kV/14 kHz. The influence of the operating frequency over the ozone generated by a DBD-plasma reactor is studied by varying the frequency in the range 8-20 kHz. The correlation between power measurements and ozone concentrations as well as ozone quenching effects at extreme power conditions are also discussed.