Impact of supercooled droplets on nanoengineered surfaces

Ice formation is commonplace in nature and manmade applications and it also influences our lives positively and sometimes catastrophically. However, a clear understanding of ice formation, role of substrate/surface on which it forms are subjects of very vigorous  current research. Icing in dynamic conditions, such as freezing of a cold drop upon hitting a surface or freezing in the presence of airflow are even less understood, despite a few novel insights developed in the last five years. This presentation will start by summarising some open and closed questions on ice formation on surfaces using nucleation theory and its extensions and report on a number of experiments to this end, which use droplet/substrate system as a model. To this end we will discuss the role of surface nanoengineering and wettability control in controlling the ice nucleation. Insights into design of icephobic surfaces with exceptional ability to delay ice formation will also be shared. The role of environmental variables such as humidity an air flow will also be discussed. Next, for the majority of the presentation, we will consider the dynamic problem of droplet and jet impacting on such surfaces reaching speeds up to ~30 m/s and Weber numbers >10,000. Droplet supercooling and its effect on droplet impact dynamics will be analysed in detail. In addition, surface morphology needs and our initial results on surface durability testing will also be presented.