Insight on the evaporation dynamics in reducing the COVID-19 infection triggered by respiratory droplets.

In this paper, the lifetime of coronavirus infected droplets under a stick-slip evaporation mode has been investigated, which may play a pivotal role in reducing the spread of COVID-19 infection. It is showed that the survival time of the virus can be reduced by increasing the receding contact angle or by reducing the initial contact angle of a drop deposited on a solid surface. It has been found that the lifetime of the virus increases almost five times under highly humid conditions as compared to dry conditions. It is further observed that the normalized lifetime does not depend upon thermo-physical properties, ambient temperature, relative humidity, and initial drop volume. A model has been proposed to estimate the shear stress acting on a virus taking into account the effect of a Marangoni flow. The presented model unveils that the magnitude of computed shear stress is not enough to obliterate the virus. The findings of the present model have been discussed in the context of reducing the COVID-19 infection, but the model can also be applied for coughed/sneezed droplets of other infectious diseases. Moreover, this physical understanding of evaporation dynamics on solid surfaces with a stick-slip mode may help in better design of a face mask, PPE kit, and other protective equipment used in public places in order to minimize the chances of infection and tackle the current pandemic. However, the reported model for estimating the survival time of the virus does not consider the effect of the thermo-capillary convection (the Marangoni effect).