Splash characteristics of ethanol-water mixture droplets impacting on superhydrophobic surfaces
The dynamic behavior of ethanol-water mixture droplets impacting on superhydrophobic surfaces with micro/nano structures was observed using high-speed photography.This study analyzed the splash characteristics of a single droplet impacting a superhydrophobic surface and investigated the effects of ethanol concentration and the Weber number(We)on the droplet dynamic evolution.The experimental results indicate that the surface wettability has only a minor effect on the maximum spreading factor and the spreading time.With increasing ethanol concentration,the static contact angle between the droplet and the solid surface decreases,while the minimum Weber number required for droplet splashing gradually increases.When the intrinsic contact angle is below 90°,the droplet is in the Wenzel state after impacting the micro-nano structured surface,which causes the disappearance of the retraction and rebound after the droplet spreading,and the sharp increase in the Weber number required for droplet fragmentation.
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