During the COVID-19 pandemic, people have become accustomed to wearing face masks, but they have a lot of fragile coverage and are not easily disinfected. Metal stems are stable, and their small pores and large surface areas suggest that they could filter out microbes. Now, researchers report in ACS ‘ Nano Letters they have converted copper nanowires into metal gases that could be used in front grooves and air filtration systems. The stems filter efficiently, decompose easily for reuse and are recyclable.
When a person with a respiratory infection, such as SARS-CoV-2, coughs or sneezes, they release small droplets and aerosolized particles into the air. Materials less than 0.3 µm can stay in the air for hours, so materials that capture these small grains are ideal for use in face masks and air filters. However, some existing filtration products have disadvantages. For example, fiberglass, carbon nanotubes and polypropylene fibers are not durable enough to undergo decontamination methods again, and some rely more on electrostatics to prevent washing, lead to a lot of waste.
Recently, researchers have developed a metallic filler with microscopic pores that is stronger and more resistant to deformation, solvents, and high temperatures and pressures. So Kai Liu and his colleagues wanted to develop and test copper foil to see if they could remove submicron-sized aerosols while also being stable enough to be used. be decontaminated and reused.
The researchers fabricated metal nails by cutting electrodeposited copper nanowires and throwing them into a stand-alone 3D network, which was reinforced with heat to form strong connections. A second copper coating was added to further strengthen the material. In experiments, the copper foam retained its shape when under pressure and at high air speeds, suggesting that it is durable for reusable face mask or air filters and could be cleaned by washing or tight air.
The team found that the metal gases had excellent filtration efficiency for particles within a size range of 0.1–1.6 µm, which is relevant for SARS-CoV-2 filtration. Their most effective material was a 2.5 mm-thick version, with copper accounting for 15% of the volume. This foam had a large surface area and captured 97% of 0.1-0.4 µm aerosolized salt grains, which are commonly used in face tests. According to the team’s calculations, breathability was comparable to the commercially available polypropylene N95 resistance. As the new material is copper-based, the filters should be resistant to cleaning agents, allow for many disinfection options, and its non-chemical properties will help kill trapped bacteria and viruses, says the researchers. In addition, they are recyclable.
The researchers estimate that the products currently cost around $ 2 per mask, and disinfection and reuse would extend their life, making them economically competitive with the usual products. .
Source:
Chemical Society of America (ACS)
Magazine Reference:
Malloy, J., et al. (2021) Efficient and Robust Metal Nanowire Foams for deep submicrometer filtration. Nano Letters. doi.org/10.1021/acs.nanolett.1c00050.