Particle convection in an evaporating colloidal droplet

emergent technique of patterning surfaces with solid particles utilizes the evaporation of colloidal droplets from a substrate. Upon complete evaporation of the liquid, the suspended particles remain adhered to the solid in a variety of patterns. Experimentally, the type of particle deposit has been correlated with the mode of liquid evaporation. It is expected that the manner in which the liquid evaporates from the droplet should significantly affect the flow of fluid inside the droplet. Therefore, the determination of the flow profiles in the droplet will aid in understanding the redistribution of particles under different experimental conditions. Using lubrication theory, this study shows that either an outward flow toward the contact line or an inward flow toward the center of the droplet can be induced, depending on the evaporative driving force. If an outward flow toward the contact line is generated inside the droplet, then a ringlike deposit remains on the substrate. Conversely, if the liquid inside the droplet flows away from the contact line, then a more uniform solute deposit will adhere to the solid.