Stability of Respiratory-Like Droplets under Evaporation
ORAL
Abstract
Enveloped viruses contained in airborne respiratory droplets have been seen to lose infectability fastest at intermediate ambient relative humidities Hr. However, the precise physico-chemical mechanisms that generate such least-favorable conditions for the virus are not fully understood yet. Analyzing the evaporation dynamics of respiratory-like droplets in air, we reveal that at high Hr, the salt dissolved in respiratory drops inhibits their evaporation indefinitely. Conversely, at low Hr the drop evaporates leaving a porous solid residue inside which virions may remain dormant for long times. The optimal Hr for the fastest reduction of the infectability lies in between, in line with the empirical evidence for the corona virus transmission probability. Finally, we use electron microscopy to examine the structure of the solid residue left upon the drop evaporates completely.
*The authors thank E.J.W. Berenschot and N. Tas for supplying the superhydrophobic substrates used in this paper. AM and CS acknowledge financial support from the European Research Council, project 678573. JRR acknowledges funding from the Spanish Ministry of Science and Innovation/Agencia Estatal de Investigación grant PID2020-114945RB-C21, partly funded through European funds, and discussions with Dr. Fernando Usera, from the Spanish CSIC/CNB. DL acknowledges discussions with Mariette Knaap and funding from the Netherlands Organisation for Health Research and Development (ZonMW), project number 10430012010022, and from the European Research Council, project 740479.
