Lifetime of sessile saliva droplets in the context of SARS-CoV-2

TL;DR

This paper develops a diffusion-based model to estimate saliva droplet drying times considering environmental factors and saliva composition, crucial for understanding COVID-19 surface transmission.

Contribution

It introduces a novel theoretical model that accounts for saliva's complex composition and dynamic contact angles to predict droplet evaporation times.

Findings

Saliva composition significantly affects evaporation rate.

Environmental conditions like humidity and temperature influence drying time.

Model provides insights into virus persistence on surfaces.

Abstract

Spreading of respiratory diseases, such as COVID-19, from contaminated surfaces is dependent on the drying time of the deposited droplets containing the virus. The evaporation rate depends on environmental conditions, such as ambient temperature and relative humidity and physical properties (e.g., droplet volume, contact angle and composition). The respiratory droplets contain salt (NaCl), protein (mucin), and surfactant (dipalmitoylphosphatidylcholine) in addition to water, which are expected to influence the evaporation in a big way. A diffusion-based theoretical model for estimating the drying time is developed which takes into account the dynamic contact angle of saliva droplets laden with salt and insoluble surfactants. The effect of the initial volume, contact angle, salinity, surfactant concentration, ambient temperature and relative humidity on the drying time of droplets is investigated.