Superhydrophobic and Self-Sterilizing Surgical Masks Spray-Coated with Carbon Nanotubes

Coronavirus has affected the entire global community owing to its transmission through respiratory droplets. This has led to the mandatory usage of surgical masks for protection against this lethal virus in many countries. However, the currently available disposable surgical masks have limitations in terms of their hydrophobicity and reusability. Here, we report a single-step spray-coating technique for the formation of a superhydrophobic layer of single-walled carbon nanotubes (SWCNTs) on a meltblown polypropylene (PP) surgical mask. The sprayed SWCNTs form a nanospike-like architecture on the PP surface, increasing the static contact angle for water from 113.6 degrees +/- 3.0 degrees to 156.2 degrees +/- 1.8 degrees and showing superhydrophobicity for various body fluids such as urine, tears, blood, sweat, and saliva. The CNT-coated surgical masks also display an outstanding photothermal response with an increase in their surface temperature to more than 90 degrees C within 30 s of 1 sun solar illumination, confirming its self-sterilization ability. Owing to the cumulative effect of the superhydrophobicity and photothermal performance of the SWCNTs, the CNT-coated masks show 99.99% higher bactericidal performance toward Escherichia coli than pristine masks. Further, the virucidal ability of the SWCNT-coated mask, tested by using virus-like particles, was found to be almost 99% under solar illumination. As the spray-coating method is easily scalable, the nanotube-coated mask provides cost-effective personal protection against respiratory diseases.