Video Explainers
A water droplet will levitate on top of a very oven tray--this is called the Leidenfrost effect. This occurs because the high temperature of the solid causes a very quick vaporization of a liquid vapour cushion, on which the droplet rests. The same effect happens for dry ice on a hot surface, and leads to levitating dry-ice blocks.
We are studying ways to create rotational motion for Leidenfrost water drops and dry-ice blocks. We achieve this by shaping the hot solid into a turbine shape, which we are currently investigating as a new means of energy conversion.
Liquid dewetting--the opposite of liquid spreading--is a fundamental process in wetting dynamics. We are looking, for the first time, at the full dewetting process of a circular film into a single droplet.
In the lab, we use "electrowetting" to force a liquid to spread on a solid surface, and then observe it relax back to its equilibrium droplet shape. Our results show that dewetting is not the opposite of spreading, and they are shedding light on the timescale that liquids need to retract from a solid surface, which has applications in printing, coating, and drying.
Surface pinning is the main source of static friction in capillary systems. When a droplet evaporates, pinning leads to the formation of watermarks by virtue of the "coffee-ring effect".
We are investigating the evaporation of droplets on Lubricant-Impregnated Rough Surfaces (LIRS), which are equipped with a thin lubricant layer that eliminates pinning. We have found a new mode of evaportion on curved LIRS, which is governed by a series of bifurcations of the shape of the droplet promoted by the shape of the solid and facilitated by the absence of pinning.