Analysis of vapor-driven solutal Marangoni flows inside a sessile droplet

Abstract

We study experimentally and theoretically how vapor-driven solutal Marangoni flows inside a sessile droplet are created. To measure the flow field, we perform a conventional particle image velocimetry (PIV). We show that the internal flow pattern can be controlled by the position and number of volatile liquid sources. To explain the mechanism, we develop a theoretical model based on Stokes flow, which predicts primary flow structures of experimental results. From the current study, we find two main conditions to determine the internal flow that are the distribution of the vapor molecules and the surface tension values depending on the concentration of the volatile liquid. From the analytical model, we successfully explain the mechanism of the solutal Marangoni flows induced by the volatile liquid components next to the sessile droplet, which can be used for optimization of the vapor-driven solutal Marangoni flow control and mixing.