Evaporation-driven directed motion of droplets on the glass

Manipulating and guiding the droplet movement on a substrate by vapor-mediated actuation is a new approach for microfluidic devices. In this work, the evaporation-driven self-propulsion of the droplets such as N,N-dimethylacetamide, and N-methylformamide on the glass is demonstrated. By the addition of the Silwet sur-factant, the aforementioned liquids change from total wetting to partial wetting and the two-component droplet is formed on the glass. The random walk behavior of the droplet can be directed by the linear and octagonal runways on a substrate, of which both hydrophobic sides are constructed by the polysilazane coating. The long -range transport of the droplet is observed, and the effect of the Silwet concentration on the self-propelled velocity is examined. Finally, the evaporation-driven mechanism is investigated by employing the open and closed en-vironments for one-droplet and two-droplet systems. It is found that the self-propelled behavior of Silwet-laden droplets vanishes in the closed environment.

Automated summary

Manipulating and guiding droplet movement on a substrate using vapor-mediated actuation is a novel approach for microfluidic devices. This study demonstrates the self-propulsion of droplets such as N,N-dimethylacetamide and N-methylformamide on glass through evaporation-driven mechanisms. By adding Silwet surfactant, the wetting behavior of the liquids changes and two-component droplets are formed on the glass. The random walk behavior of the droplets can be directed by hydrophobic runways on the substrate, and the long-range transport of the droplets is observed. The effect of Silwet concentration on self-propelled velocity is examined, and the evaporation-driven mechanism is investigated in open and closed environments.