The contact time of droplets impacting on macroscopic anisotropic superhydrophobic surfaces (macro-aniso-SHSs) decreases with an increase in the spacing and the underlying mechanism includes the mass distribution and the momentum anisotropy induced by the parralel macrostripes and macrogrooves. As the figure shows, although the impacting drop on the macro-aniso-SHS with a narrow spacing (400āĪ¼m) cannot be divided by the stripes, the anisotropy of the surface concentrates the momentum in the direction parallel to the stripes, leading to breakup and thus reducing the contact time by 15ā30% compared with the contact time on the SHS and micro-aniso-SHS. For macro-aniso-SHSs with wide spacing of 1200āĪ¼m, the contact time is reduced by 40ā50%. The contact time for an impact centered on the stripe is not significantly different from that in the groove, whereas the impact centered in the groove produces new hydrodynamics characterized by extended spreading, easy break-up, and flying-eagle behavior. We envision that understanding the droplet behavior on macro-aniso-SHSs not only extends our fundamental understanding of classical impacting phenomena but also has potential for a broad range of applications, such as anti-icing, self-cleaning and heating transfer.
- Meirong Song
- Zhaohui Liu
- Lei Jiang
