Dr Marc Pradas

Droplets interacting with solid surfaces are found in a wide variety of daily life experiences and natural phenomena. Their study serves as a canonical example of a wetting phenomenon which, despite its simplicity, has been shown to be a remarkably complicated problem. Many theoretical efforts over the last few years have focused their attention on understanding how the properties of the solid surface affect the dynamics of the droplet, with particular emphasis on droplet control and manipulation, which is important for a wide range of technological applications, such as liquid-repellent surfaces, micro chemical reactors and fluid transport processes, and the rapidly growing fields of Nano- and micro-fluidics. Quite often the volume of the droplets is subject to external, time-dependent variations - a situation that we refer to as droplets with dynamic size. This occurs, for example, when there is mass exchange through the droplet interface (evaporation/condensation phenomena), or when droplets sit on porous materials so that liquid is absorbed through the pores. This project will explore the fundamental interplay between a time-dependent variation of the droplet volume and simple smooth variations on solid surfaces. We aim to investigate under which conditions a droplet may naturally exhibit lateral motion as its volume changes in time, and to exploit this in applications on droplet control, such as directed motion. The ultimate goal of the proposed research is the systematic and predictive theoretical and computational analysis of the dynamics of droplets with dynamic size on surfaces that have controllable and experimentally amenable properties. As a consequence, the outputs of this project can be used to recommend new design rules, geometries, and operational protocols for improved droplet control and manipulation in technological applications that rely on cooling/heating processes and/or porous-based micro-devices.