Tunable Droplet Breakup Dynamics on Micropillared Superhydrophobic Surfaces

Functional materials with controllable droplet breakup properties have extensive application prospects in aircraft anti-icing, spraying cooling, surface coating, and so on. Here we show that introducing micropillar arrays with various morphologies to fabricate superhydrophobic surfaces could either facilitate or suppress droplet splitting. The spacing and height of micropillars play an essential role in tuning the splitting patterns. Delayed splashing occurs on dense pillars which support the liquid lamella and provide channels for air to escape. A novel droplet breakup mechanism is found on sparse tall pillars, which rises from the instability of lateral liquid jets and significantly reduces the droplet breakup threshold. The critical Weber number of the rupture of low-viscous liquid is solely determined by the geometric parameters of micropillars and droplets. This work unveils the impact of ordered microstructures on the droplet breakup dynamics and provides a quantitative analysis of the geometric parameters in revising the breakup criteria.