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

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

To allow an efficient protection against viruses like the severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), it is important to avoid their spreading by using filtering face pieces (FFP), which are categorized by different standards according to their filtration efficiency. In this study, we subjected six brands of FFP2 standard masks to three different conditions and subsequently analysed them for their filtration performance to evaluate potentials for reusability. The conditions comprised changes of temperature and air humidity, an exposure to isopropyl alcohol (IPA) and an autoclave sterilization. While four of six masks consisted of electrostatically treated melt blown non-wovens, two masks were fabricated using a nanofibrous multilayer system. Due to the absence of prior electrostatic treatment, the nano-masks did not show a significant change in filtration efficiency when discharged by IPA, unlike the melt blown nonwoven masks showing a significant decrease of filtration efficiency down to around 50% at a particle size of 0.3 μm. However, most melt blown masks maintained a sufficient filtration efficiency after all other treatments with even better results than the nanofibrous masks. This was particularly the case for the capacity to filter smallest particles/droplets with a size of around 0.1 μm, which is below the range of typical filtering standards and important for the retention of virally contaminated nano-aerosols or unattached viruses. After temperature/humidity variation and autoclave sterilization, melt blown masks were able to retain a filtration efficiency up to over 90% at 0.1 μm contrary to nano-masks showing a decrease down to around 70%. Based on their better filtration performance, lower price and potential reusability, we conclude that electret melt blown masks are the preferable type of FFP2 masks.

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

In the present study, electrospun nanofibers of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), a biodegradable polyester, containing natural deep eutectic solvents (NADES) were obtained and reported for the first time, exhibiting an unreported 3D morphology and enhanced charge retention properties. Choline chloride (ChCl)/urea/water in a molar ratio of 1:2:1 was used as the NADES model system. Electrospun nanofibers were produced from a 10 wt % solution of PHBV containing 26 wt % NADES with respect to the polymer and were deposited on different substrates, that is, aluminum foil and non-woven spunbond polypropylene (PP). The morphology and charge retention ability were characterized under different conditions and on different substrates. The attained fiber morphology for the NADES-containing mats showed an average fiber diameter of around 300 nm, whereas the pure PHBV polymer under the same conditions produced electrospun fibers of around 880 nm. However, the deposition of PHBV/ChCl/urea/water fibers resulted in a surprising macroscopic rugose 3D surface morphology made of aligned nanofibers when processed at 50% relative humidity (RH). The nanofiber grammages above which this 3D morphology, associated with NADES-induced charge retention, formed was found to be dependent on the substrate used and RH. This morphology was not seen at 20% RH nor when pure PHBV was produced. Charge stability studies revealed that PHBV/ChCl/urea/water nanofibers exhibited lasting charge retention, especially when sandwiched between spunbond polypropylene textiles. Finally, such multilayer structures containing a very thin double layer of PHBV/ChCl/urea/water fibers after corona treatment exhibited improved paraffin aerosol penetration, which was ascribed to the combination of thinner fibers and their charge retention capacity. The here-developed electrospun PHBV fibers containing NADES demonstrated for the first time a new potential application as electret filter media.

Worldwide fight against COVID-19 using nanotechnology, polymer science, and 3D printing technology

One of the lethal illnesses that humanity has ever seen is COVID-19 irrefutably. The speed of virus spread is high and happens through polluted surfaces, respiratory droplets, and bodily fluids. It was found that without an efficient vaccine or specific treatment using personal protective equipment, preventing contamination of hands, and social distancing are the best ways to stay safe during the present pandemic. In this line, polymers, nanotechnology, and additive manufacturing, or 3D printing technology have been considered to probe, sense, and treat COVID-19. All aforementioned fields showed undeniable roles during the COVID-19 pandemic, which their contributions have been reviewed here. Finally, the effect of COVID-19 on the environment, alongside its positive and negative effects has been mentioned.

Effective antiviral coatings for deactivating SARS-CoV-2 virus on N95 respirator masks or filters

The application of antiviral coatings to masks and respirators is a potential mitigating step toward reducing viral transmission during the SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) pandemic. The use of appropriate masks, social distancing, and vaccines is the immediate solution for limiting the viral spread and protecting people from this virus. N95 respirator masks are effective in filtering the virus particles, but they cannot kill or deactivate the virus. We report a possible approach to deactivating SARS-CoV-2 by applying an antimicrobial coating (Goldshield 75) to masks and respirators, rendering them suitable for repeated use. Masks coated with Goldshield 75 demonstrated continuous inactivation of the Alpha and Beta variants of the SARS-CoV-2 over a 3-day period and no loss of inactivation when stored at temperatures at 50 °C.

Impact of COVID-19 on materials science research innovation and related pandemic response

ABSTRACT

The scope of impact that the coronavirus SARS-CoV-2 has had and continues to have on life, society, and the world as we know it will be debated for years to come. One thing is for certain, scientists, engineers, clinicians, and researchers around the globe rallied to heed the call for innovation, particularly in the field of materials science. In this special issue of MRS Bulletin, we feature six articles, two of which showcase primary consumable materials research and development, along with four review articles highlighting materials innovation over the last 18 months in diagnostics, prevention, and treatment of SARS-CoV-2 infection.

GRAPHIC ABSTRACT