The project is with Prof Jian from WUStL, Joint Masters Programme
Airborne particles and droplets have come to play a major role in the three most pressing problems faced by humanity today: climate change, health effects of air pollution, and propagation of air-borne diseases such as COVID-19. Cloud droplets offer significant uncertainty in predicting climate change and cough droplets contain the key to understanding the spreading of airborne respiratory diseases. While considerable research has been taking place, a detailed understanding of the formation, evolution and evaporation of cloud droplets, formation of residues, interaction with ions and aerosols, and the role of these processes on precipitation is lacking. Similarly, as we saw recently during the Covid-19 outbreak, there is a considerable lack of knowledge on the behaviour of virus laden cough droplets in indoor and outdoor atmospheres. Added to this is the alarming situation with respect to air pollution which is causing the annual death of millions today in the world.
A significant part of the knowledge gap in droplet and particle behaviour can be bridged by studying the single partlcle microphysical processes under controlled conditions. Particle levitation technology offers an excellent approach to achieve this. To trap charged particles and droplets in the size range of 30-200mm, a quadrupolar trap (also known as the Paul trap) based on electrodynamical principles was developed in the department of chemical engineering in IITB in the last few years. In order to study large uncharged particles in the range of 1- 4 mm, an acoustic trap has been developed through a joint programme between IITB and Washing University in Saint Louis, USA. The latter is conceived to be particularly useful to study droplet to ice phase transitions, the behaviour of bioaerosol systems such as the bursting of pollen as well as cough droplets.
Given these motivations, the objective of this project is to develop a system that can levitate individual droplets and aerosol particles, independent of the influence of chamber walls, for long periods of time (hours) under a wide range of conditions (e.g., temperature, relative humidity, and pressure). The system is also capable of optically characterizing the droplet size, its course of evolution and phase transition during ice particle formation. The study will involve high speed imaging as well as detecting scattered light signals. The system is also capable of optically characterizing the droplet size, its course of evolution and phase transition during ice particle formation. Specifically, both Paul traps and acoustic levitators will be customized to examine a host of phenomena relevant to cloud droplets, bioaerosols and air cleaning technology. It is expected that the development will enable the investigation of formation, growth, and evaporation of ice particles, secondary ice formation, reduction of expiratory droplets to residues, and the survival probability of pathogens in airborne droplets.