Abstract
During the COVID-19 pandemic, the mandatory use of multiple surgical masks or N95 respirators in public raised concerns about potential health issues associated with the increased breathing force needed to maintain the breathing cycle. To address these concerns, we conducted a comprehensive study investigating the transportation and filtering mechanisms of heterogeneous nanoparticles and virus-like particles through surgical masks and N95 respirators. Our multifaceted approach combined in vitro experiments utilising aerosol spray paints containing nanoparticles and in vivo validation on human volunteer inhaling city air. We employed scanning electron microscopy and transmission electron microscopy to analyse the distribution of nanoparticles across various mask layers and pristine silicon substrates placed on human skin. In addition, we provide analytical insights into the pressure distribution and fluid velocity profiles within the complex polymer fibre network of the masks. Our findings remarkably revealed that both single surgical masks and N95 respirators exhibited similar nanofluidic performance in filtering colloidal and jet-stream nanoparticles in the air. These results have significant implications for policymakers in developing regulations to manage airborne pandemics and air pollution control, ultimately enhancing public health and safety during respiratory health crises.