Disinfection and Electrostatic Recovery of N95 Respirators by Corona Discharge for Safe Reuse

Abstract

With the COVID-19 pandemic surging, the demand for masks is challenging, especially in less-developed areas across the world. Billions of used masks are threatening the environment as a new source of plastic pollution. In this paper, corona discharge (CD) was explored as a safe and reliable method for mask reuse to alleviate the situation. CD can disinfect masks and simultaneously restore electrostatic charges to prevent filtration efficiency deterioration. Electric field, ions, and reactive species generated by CD cause DNA damage and protein denaturation to effectively disinfect N95 respirators. Log reduction of 2−3 against Escherichia coli can be easily reached within 7.5 min. Log reduction of up to 6 can be reached after three cycles of treatment with optimized parameters. CD disinfection is a broad spectrum with log reduction >1 against yeast and >2.5 against spores. N95 respirators can be recharged within 30 s of treatment and the charges can be retained at a higher level than brand-new masks for at least 5 days. The filtration efficiency of masks was maintained at ∼95% after 15 cycles of treatment. CD can provide at least 10 cycles of safe reuse with benefits of high safety, affordability, accessibility, and device scalability/portability.

Nonthermal Plasma Effects on Fungi: Applications, Fungal Responses, and Future Perspectives

“…Corona discharges can be operated in direct current or pulsed mode, where the pointed electrode has a negative or positive potential [ 9 ]. Corona discharges are used in various industrial applications [ 16 , 17 , 18 , 19 , 20 , 21 ].…”

Automated corona discharge (CD) for efficient and broad-spectrum surface and air sterilization

“…Based on our previous results in ref. 25, the discharge voltage and current were respectively set at 25 kV and 0.05 mA, meaning the output power is as low as 1.25 W. The tested surfaces include cloth masks, face shields made of polyethylene terephthalate (PET), coveralls made of polypropylene (PP), alumina, which represents most ceramic surfaces, and stainless steel, which represents conductive surfaces. The specimens were cut into 5 cm by 5 cm squares and then mounted on the ground electrode made from a stainless-steel plate.…”

“…In our previous research, we have confirmed the capability of corona discharge (CD) for the safe reuse of N95 respirators by disinfecting and recharging them simultaneously. 25 This technology can address the mask shortage problem and reduce the environmental impact of disposing of used masks. Additionally, we observed cell membrane rupturing and tested DNA damage in the sterilization mechanism of CD.…”

Importance of Dipole Orientation in Electrostatic Aerosol Filtration

“…Airborne particles can be captured by a fiber via four well-known mechanisms: Brownian diffusion, inertial impaction, interception, and electrostatic attraction . In this study, we only focus on the electrostatic attraction for its importance in modern-day filtration media (e.g., N95 respirators and surgical facemasks, which are normally certified using NaCl particles in the size range of 20–500 nm) − and as other mechanisms have been studied extensively in past studies. − Our study is aimed at calculating the SFE of a bipolarly charged fiber. Only two extreme dipole orientations parallel to the flow and perpendicular to the flow are considered.…”

“…Here, Kn f = 2λ/ d f is the fiber Knudson number and d f and λ are the fiber diameter and the MFP of the air molecules, respectively. Most facemasks and respirators (e.g., N95 masks) are made of melt-blown and spun-bond fibers with a diameter in the range of 4–16 μm. − , With fibers ranging from 4 to 16 μm in diameter and λ = 65 nm in atmospheric conditions, the slip flow regime is expected to prevail in the flow domain. Therefore, the aerodynamic slip at the fiber surface was incorporated in our simulations by means of a user-defined function (UDF) (see refs − for more details).…”