Using Aerosolized Silicon Nanoparticles Towards Development of Masks Designed to Filter Specific Viruses

A highly contagious respiratory virus called SARS-CoV-2 immerged in Wuhan, China in end of 2019. It initiated a world-wide pandemic in 2020 (COVID-19). Countries took extreme actions to avoid the transmission of such virus by implying restrictions in wearing personal protective equipment, which includes wearing masks. According to epidemiologists the main reason behind the spread of this viral disease is sneezing and coughing, rendering the wearing of masks highly important for personal protection. Masks are usually used to prevent the transmission of pathogenic microorganisms from symptomatic and asymptomatic carriers to those who are in contact with them, wherein the mask filters the microorganisms from getting into the respiratory secretions. A common type of mask that is used due to its wide availability is the polyethylene (PE) filter mask. However, maks filter virus by the size only and not by its biological or chemical nature. Imagine we can design a mask that can 100 % filter SARS-CoV-2 or any other future virus. It would be a game changer for front line workers and can help end pandemics very fast without the need for exteme measures. Using nano technology this future may be possible. Here we will aim to demonstate an intial proof of concept of such a filter using nano particles. 3 nm silicon nanoparticles (Si-NPs) were used to model the SARS-CoV-2. The specific Si-NPs were chosen due to their chemical activity, ultra-small nature, easy attachment to other materials through chemical bonding, high luminescence and hydrophobicity, which makes clusters of diameters of 100-300 nm, which is similar to the virus size. Both N95 and surgical masks are investigated in this work using the Si-NPs. In the study Si-NPs were used to examine the filtering process of the mask. Si NPs were fabricated by chemical etching of boron-doped 100 Si wafers. The process has been described in [The developed Si-NPs were dispersed in isopropyl alcohol (IPA) and filled into spraying bottle. The spraying bottle produces a cloud of droplets ranging from 40 to 900 mm, which is used to mimic the sneeze, where the droplets size is between 20 to 900 mm per spray. Testing the spraying was done on a Si wafer under UV radiation to picture the dropping pattern of the particles on the surface. To visualize the filtering process of the mask, we placed the mask between the prepared spraying bottle and 3x3 cm Si wafer that is mounted over a foam surface and above table surface. The testing conditions were carried in constant mode. The N95 mask fibers were studied by optical imaging and scanning electron microscopy imaging. The SEM image show that the fibers have diameter of about 25 mm and that the roughness and surface typography is random. The figure also shows two setups mask with and without Si-NPs. The mask fibers trap the Si-NPs creating clusters of fibers around it, which is not detected in the mask without the NPs. To examine the mask under UV, a luminescence image was taken for the mask with NPs and without NPs. The image shows bright red/orange luminescence for the mask with NPs, which indicates nano particles bonded to the fibers as a SARS-CoV-2 would do. A section of the N95 mask was taken and studied under UV light. The mask with the sprayed NPs showed very bright luminescence emitted from the mask fibers, which is not noticed without the NPs. We take images of the mask fibers under luminescent microscopy. To summarize, aerosolized Si nanoparticles were used visualize how mask are used to filter out a nano scale virus. A setup was created to test the mask, where Si-NPs were sprayed on to the mask from certain distance and a UV- induced fluorescence was used to observe the NPs being sprayed and reaching masks. The study showed that mask fibers are good at filtering nano-scale virus that led to infections. Morever, this indicates the possibilty of a future where we can design masks to filter out specific virus which will reduce infections.