Penetration and Secondary Atomization of Droplets Impacted on Wet Facemasks

TL;DR

This study investigates how wetness affects droplet penetration and atomization on different mask types, providing insights into mask efficacy when wet, which is less understood compared to dry masks.

Contribution

It offers the first experimental analysis of droplet impact dynamics on wet masks, comparing hydrophobic and hydrophilic materials to understand penetration mechanisms.

Findings

Wetness influences droplet penetration and atomization.

Hydrophobic and hydrophilic masks exhibit different impact behaviors.

Sequential impacts increase the risk of droplet penetration.

Abstract

Face covering, commonly known as facemask, is considered to be one of the most effective Personal Protective Equipments (PPEs) to reduce transmissions of pathogens through respiratory droplets - both large drops and liquid aerosol particles. Face masks, not only inhibit the expulsion of such respiratory droplets from the user, but also protects the user from inhaling pathogen-laden potentially harmful droplets or their dried nuclei. While the efficacies of various dry face masks have been explored in the recent past, a comprehensive investigation of a wet mask is lacking. Yet, users wear masks for a long period of time and during this period, owing to respiratory droplets released through multiple respiratory events, the mask matrix becomes wet. We, herein, present an experimental study on the dynamics of sequential impacts of droplets on masks to understand how wetness affects possible penetration and secondary atomization of the impacted droplet. Two different types of masks, hydrophobic and hydrophilic, were used in this study to evaluate the underlying physical mechanism that controls the penetration in each of them.