Abstract
Abstract
Highlights
Evaporation of sessile droplets has attracted a lot of attention over the past decades due to its ubiquitousness and huge relevance for various applications, such as inkjet printing (Park & Moon 2006), surface patterning (Kuang, Wang & Song 2014) and microfabrication (Kong et al 2014), among others
We experimentally demonstrated that gravitational effects dominate the flow structure in the droplet system, due to the suppression of Marangoni flow by the instantaneous segregation of 1,2-hexanediol close to the contact line
The observation shows an instantaneous segregation of 1,2-hexanediol in the sessile droplet followed by the formation of plumes of the segregated fluid
Summary
Evaporation of sessile droplets has attracted a lot of attention over the past decades due to its ubiquitousness and huge relevance for various applications, such as inkjet printing (Park & Moon 2006), surface patterning (Kuang, Wang & Song 2014) and microfabrication (Kong et al 2014), among others. While the evaporation of single-component droplets is relatively well understood (Hu & Larson 2002; Popov 2005; Ristenpart et al 2007; Cazabat & Guéna 2010; Gelderblom et al 2011; Marin et al 2011; Lohse & Zhang 2015; Chong et al 2020), multicomponent droplets show far more complex dynamics during the drying process This is due to the complicated coupling of the mutual interactions between species (Brenn et al 2007; Chu & Prosperetti 2016; Diddens et al 2017) and the resulting flow structures (Kim et al 2016; Karpitschka, Liebig & Riegler 2017; Marin et al 2019). Very recently, Edwards et al (2018) and Li et al (2019) found gravity-driven flows in different binary microdroplet systems, which are triggered by the density gradients from the selective evaporation This is the first evidence that buoyancy-driven Rayleigh convection can overcome Marangoni flow in controlling the flow structure in such evaporating liquid-mixture droplets with Bond number Bo 1. The paper ends with a summary and an outlook for future work (§ 5)
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