Recent developments in filtration media and respirator technology in response to COVID-19

Abstract

The COVID-19 pandemic triggered a surge in demand for N95 or equivalent respirators that the global supply chain was unable to satisfy. This shortage in critical equipment has inspired research that addresses the immediate problems and has accelerated the development of the next-generation filtration media and respirators. This article provides a brief review of the most recent work with regard to face respirators and filtration media. We discuss filtration efficiency of the widely utilized cloth masks. Next, the sterilization of and reuse of existing N95 respirators to extend the existing stockpile is discussed. To expand near-term supplies, optimization of current manufacturing methods, such as melt-blown processes and electrospinning, has been explored. Future manufacturing methods have been investigated to address long-term supply shortages. Novel materials with antiviral and sterilizable properties with the ability for multiple reuses have been developed and will contribute to the development of the next generation of longer lasting multi-use N95 respirators. Finally, additively manufactured respirators are reviewed, which enable a rapidly deployable source of reusable respirators that can use any filtration fabric. Graphic abstract

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Electrospun Nanofibers Containing Natural Deep Eutectic Solvents Exhibiting a 3D Rugose Morphology and Charge Retention Properties

“…The typical N95 respirator is a good example for this, consisting of two or three piles of a dielectric material layer with a quasipermanent electrical charge (electrostatic filtration layer) between two layers of spunbond polypropylene. 10 However, the polypropylene layers used in respirators are thick petroleum-derived filtration materials, and new alternatives with higher filtration efficiency per grammage are of interest, in that they may potentially improve sustainability by both reducing material consumption and having alternative end-oflife scenarios such as organic recycling when made of biodegradable polymers. 12 Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a biobased and biodegradable copolymer composed of the homopolymer poly(3-hydroxybutyrate) (PHB) with hydroxyvalerate (HV) units along the backbone.…”

“…Spunbond polypropylene (PP) is widely used as a non-woven material in medical masks and respirators due to its ease of processing, much-needed mechanical strength, hydrophobicity, and lower air resistance. , However, they suffer from poor filtration performance for fine particles when used alone . In many citations relating to protective equipment, one approach to solve this drawback is to use spunbond non-woven materials as the external mechanical support for the core electrostatic filtration layer, typically made of meltblown polypropylene, that can effectively filter finer particles.…”

“…In many citations relating to protective equipment, one approach to solve this drawback is to use spunbond non-woven materials as the external mechanical support for the core electrostatic filtration layer, typically made of meltblown polypropylene, that can effectively filter finer particles. The typical N95 respirator is a good example for this, consisting of two or three piles of a dielectric material layer with a quasi-permanent electrical charge (electrostatic filtration layer) between two layers of spunbond polypropylene . However, the polypropylene layers used in respirators are thick petroleum-derived filtration materials, and new alternatives with higher filtration efficiency per grammage are of interest, in that they may potentially improve sustainability by both reducing material consumption and having alternative end-of-life scenarios such as organic recycling when made of biodegradable polymers …”

Investigation on external quantum efficiency droops and inactivation efficiencies of AlGaN-based ultraviolet-c LEDs at 265–285 nm

“…In addition to highly effective vaccines, preventing the spread of viruses remains crucial, and recommended precautions generally include social distance, wearing masks, hand washing, and disinfection among others. The surface of cargos can be disinfected by the chemical solution, such as 70% ethanol, 0.1% sodium hypochlorite or 0.5% hydrogen peroxide, or sterilized and irradiated by ultraviolet-c (UVC) light (200-280 nm) [4]. The UVC irradiation owns several promising advantages, such as safety, environmentally friendliness, and without chemical residue among others.…”

Influence of different treatment conditions on the filtration performance of conventional electret melt blown non-woven and novel nano FFP2 masks

“…The system is arranged in a so-called SMS-structure, with an upper and lower layer of spun bond and a middle layer of melt blown serving as the main filtering medium [4]. In addition to a necessary low fiber diameter of around 2-4 μm, the melt blown layer is characterized by a corona discharge to adhere droplets/particles electrostatically [3][4][5][6][7][8][9][10][11]. Both features control the filtration efficiency of the FFP2 mask [4].…”