A Flexible Nanoporous Template for the Design and Development of Reusable Anti-COVID-19 Hydrophobic Face Masks

ABSTRACT

Since the outbreak of the severe respiratory disease caused by the novel coronavirus (COVID-19), the use of face masks has become ubiquitous worldwide to control the rapid spread of this pandemic. As a result, the world is currently facing a face mask shortage, where some countries placed a limit on the number of masks that can be bought by each person. On the other hand, while the surgical grade N95 mask provides the highest level of protection up till now, its filtration efficiency for sub-300-nm particles is around 85% due to its wider pore size (~300 nm). Since the COVID-19 virus shows a diameter of around 65-125 nm, there is a need for developing more efficient masks. To overcome these issues, here, we demonstrate the development of a flexible nano-porous membrane to achieve a reusable N95 mask with a replaceable membrane and enhanced filtration efficiency. A flexible nano-porous Si-based template is first developed on a silicon-on-insulator wafer using KOH etching, the template is then used as a hard mask during a reactive ion etching process to transfer the patterns onto a flexible and lightweight (< 0.12 g) polymeric membrane. Pores with sizes down to 5-nm are achieved with a narrow distribution. Theoretical calculations show that airflow rates above 85 L/min are possible through the mask which confirms it breathability over a wide range of pore sizes, densities, membrane thicknesses and pressure drops. Finally, the membrane is intrinsically hydrophobic which contributes to anti-fouling and self-cleaning as a result of droplets rolling and sliding on the inclined mask area.