To find out how the COVID-19 virus survives on surfaces, researchers in India are exploring the drying times of thin liquid films that persist on surfaces after most respiratory droplets evaporate. While the drying time of typical respiratory droplets is on the order of seconds, the survival time of the COVID-19 virus was found to be on the order of hours. In Physics of Fluids, the researchers describe how a nanometers-thick liquid film clings to the surface, allowing the virus to survive.
Using face masks to help slow the spread of COVID-19 has been widely recommended by health professionals. This has triggered studies of the materials, design, and other issues affecting the way face masks work. In Physics of Fluids, investigators looked at research on face masks and their use and summarized what we know about the way they filter or block the virus. They also summarize design issues that still need to be addressed.
Many people reuse masks and other face coverings many times without sanitizing them. That is likely because current sanitization methods can be cumbersome. A new device using a hanging rack and UV-C light can sterilize up to six masks and other items simultaneously and quickly, killing bacteria, yeasts, mold spores, and viruses. This device has shown its efficacy against pathogens including the highly-contagious E-coli, which was eradicated in about one minute.
As the pandemic continues, researchers have increasingly focused on the extent to which respiratory droplets carrying the coronavirus travel and contaminate the air after an infected person coughs. While scientists have studied the properties of air at the mouth, less is known about how these properties change as the cough cloud travels. In Physics of Fluids, researchers estimate the evolving volume of the cough cloud and quantify the reduction in its volume in the presence of a face mask.
Engineers have incorporated a new understanding of the impact of environmental factors on droplet spread into a mathematical model that can be used to predict the early spread of respiratory viruses including COVID-19, and the role of respiratory droplets in that spread.
It is well established the COVID-19 virus is transmitted via respiratory droplets. Consequently, much research targets better understanding droplet motion and evaporation. In Physics of Fluids, researchers developed a mathematical model for the early phases of a COVID-19-like pandemic using the aerodynamics and evaporation characteristics of respiratory droplets. The researchers modeled the pandemic dynamics with a reaction mechanism and then compared the droplet cloud ejected by an infected person versus one by a healthy person.