Are rechargeable N95 masks the solution to the N95 mask shortage?

Our first line of protection against airborne particulate matter is the face masks. N95 respirators include a vital feature of the personal protection system used by healthcare staff in the frontline as they provide an obstacle to the dissemination of contaminants filled with droplets ejected by an infected person by coughing, sneezing, talking, or breathing.

For two reasons: (1) possible pollution and (2) rapid deterioration of their filtering efficiency when used N95 masks are designed for one-time use. However, with the latest COVID-19 pandemic, the masks are severely deficient and an extensive computational search has been undertaken to enable multiple uses.

Much of the literature has addressed different proposals for systems for decontamination, including the careful application of dry and wet heat or ozone, hydrogen peroxide vapor, UV, or spirit. While many of these approaches are able to deactivate viruses, it is a general understanding that filtration performance is adversely affected, and the structural integrity of the mask can also be compromised. There's no attention paid to restoring a mask's filtration ability until it gets degraded; this is the problem we discuss in this piece. In this paper, we suggest a process that can return the filtration performance to out-of-box standards if the mask isn't structurally corrupted.

Filtration Process 

N95 masks intercept foreign particles from multiple layers of the mask material, as with other filtering methods. If a particle meets a mask fiber directly on its path mechanically or electrostatically, a mask substance is capable of attracting and ensnaring particles.

The minimum filtering efficiency is 0.3 μm for particles of a minimum size in filters based on fibrous materials and working at filtration rates close to those used in human breathing. On this size, the filtration process passes from a dominated environment of diffusion to a dominated regime of inertia.

N95 respirators use an electrostatic system to attract and intercept extraneous particles as well as mechanical trapping (charged or uncharged). This occurs when the mask material has critical electrical fields and electrical field gradients, which can arise when the fibers are filled.

The filtration of N95 masks to the 95% stage is powered by these electrostatic interactions. 

Rechargeable Mask and Normal N95

The electrostatic filtration procedure is carried out on standard N95 masks by a sheet composed of charged polypropylene fibers. The highest number of pores in this mesh is roughly 15 μm, with an average of 90% free space. This layer is placed between two or more almost solid materials, supplying mechanical and supportive filtration. Polypropylene is an electret that can bear a load, or has a distinctly microscopic moment. It is a dielectric substance.

Non-polar polymers with an 8 eV band space comprise pure polypropylene. However, the presence of both physical and chemical defects at the molecular level causes distributed energy states to evolve which can trap the load. In addition, its electrical polarisation characteristics are also improved by the inclusion in the polymer melt of different additives such as Magnesium Stearate or BaTiO to boost electrode. Still, at this stage, there is a substantial deterioration of the charge of the polypropylene fibers when open to the air that is intensified by the wet, moist environment created during use by respiration. Moreover, all the charges from the loading layer with a console decrease in mass efficiency are eliminated by most decontamination methods.

So the ability of an electric mask to sustain charge in a warm and humid environment is a crucial feature of its performance. If this is not practical, intensive use can only be made of a decontamination and recharge method. Therefore, it is very convenient to recharge a decontaminated mask electrically without dismantling it, in particular, if it does not rely on special equipment that is not readily available.

Corona discharge, photo-ionization of the beams (gamma rays, x-rays, and electron beams), triboelectrification, and liquid contact charging are common techniques for charging polymer fibers.

These procedures cannot be readily used on pre assembled masks in hospital environments. In this note, we are suggesting and demonstrating its efficacy in a simple recharge technique based on high electric fields.

Our system can primarily be used in urban as well as rural settings with the aid of readily available equipment and materials.

Rechargeable Mask and Shortage of N95

N95 masks constitute a vital part of the personal protection that is used by health professionals on the frontlines. These masks achieve an efficiency of 95 percent while filtering small 0.3 microns while retaining an adequate ventilation efficiency for the use of fine polypropylene fibers with electrical charges for the attraction of particles.

Extended use and decontamination caused by extreme worldwide supply shortages during COVID-19 will quickly degrade filter performance and loading.

The Physics of Fluids journal of AIP Publishing shares a way to restore the filtration performance of N95 masks to out of box speeds, for as long as the mask is not affected. The researchers of India's Tata Institute of Fundamental Research and Israel's Technion IIIT.

As used, all masks based on electrostatics steadily lose their efficiency because of their moisture content.

The Group's work makes it possible to integrate excess charges into the material, by linking it with a battery, in high electric fields of conductivity of polypropylene. The applied electrical area becomes zero when the charging source is off and the conductivity of the polypropylene reduces to zero. This immobilizes the supplementary carriers and holds the substance charged.

The researchers have found that they can transform an N95, which greatly decreases its filtration effectiveness, into a normal washing machine to clean it. It could then be recharged by sandwiching between two high-voltage, 95% performance electrodes.

A proof-of-concept construction of a battery-operated intelligent mask is also seen, where the missing charge is regularly refilled by plugging the mask into a charging plant, close to the way your device is powered.

The group claims that its approach to filling masks contributes to highly energy-efficient intelligent masks.

Currents are in the microamp, with an incredibly low power demand of one thousand watts, so a lightweight and realistic approach can be applied shortly.

Furthermore, their system is useful for a range of applications for air filtering, including HVAC or automotive filters.

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