Anti-Icing or Deicing: Icephobicities of Superhydrophobic Surfaces with Hierarchical Structures.

Superhydrophobic surfaces have gained tremendous attention for icephobic properties, including anti-icing and deicing. The former is about how much a surface can delay the ice formation, whereas the latter is about how easy the surface can let the ice go off after freezing. In this study, superhydrophobic surfaces with different surface roughnesses and wettabilities were tested for both anti-icing and deicing purposes to investigate their correlation in association with the different surface properties. Anti-icing test was conducted by utilizing an icing wind tunnel to see how much ice gets accumulated on the surfaces in a dynamic condition (i.e., impacting supercooled water droplets by forced wind). For the deicing test, sessile droplets were frozen on the surfaces in a static condition (i.e., no wind) and then the shear adhesion forces were measured to disconnect the frozen ices off from the surfaces. The experimental results show that higher anti-icing efficacy does not necessarily mean higher deicing efficacy because of the different icing mechanisms. Although a superhydrophobic surface with a lower depinning force (or contact angle hysteresis) delays the ice accumulation in a dynamic condition more effectively, the same surface can require higher shear adhesion force for ice grown in a static condition where condensation and wetting state of a droplet are the key factors.