Stability and Retention Force Factor for Binary-Nanofluid Sessile Droplets on an Inclined Substrate

We investigate the retention force factor of sessile droplets of pure (ethanol) and binary (water-ethanol) fluids laden with alumina nanoparticles placed on a critically inclined substrate. It is observed that while the critical angle of an ethanol droplet increases with an increase in nanoparticles concentration, for water-ethanol binary droplets, it reaches to plateau and decreases slightly after 0.6 wt % nanoparticle loading. The effect of composition and concentration of nanoparticles on the retention force factor is studied, and correlations are proposed for the retention force factor and critical angle for pure and binary droplets. Infrared images of evaporating droplets of pure and binary fluids reveal richer hydrothermal waves in droplets with nanoparticle loading than in droplets without loading, and these waves are more intense in pure ethanol droplets. On an inclined substrate, the body force caused the droplets to elongate more toward the receding side, which led to an earlier breakup of the droplet at the receding side. To the best of our knowledge, our study is a first attempt to investigate the retention force factor for the droplets loaded with nanoparticles on an inclined substrate.

Automated summary

We investigated the retention force factor of pure and binary droplets laden with alumina nanoparticles placed on an inclined substrate. The critical angle of ethanol droplet increased with nanoparticles concentration, while for water-ethanol droplets, it reached a plateau and slightly decreased after 0.6 wt% nanoparticle loading. We proposed correlations for the retention force factor and critical angle and found that evaporating droplets with nanoparticle loading exhibited richer hydrothermal waves. This study is the first attempt to investigate the retention force factor for droplets loaded with nanoparticles on an inclined substrate.