  Numerous studies have focused on a low surface energy coating and a
micro/nanoscale surface texture to design functional surfaces that delay frost
formation and reduce ice adhesion. However, the scientific challenges for in
developing icephobic surfaces have not been fully addressed because of
degradation such as mechanical wearing. Inspired by the suppressed frost
formation on concave regions of natural leaves, here we report findings on the
frosting process on hydrophobic surfaces with various serrated structures.
Dropwise condensation, the first stage of frosting, is enhanced on the peaks
and suppressed in the valleys when the serrated surface is exposed to humid
air, causing frosting to initiate from the peak. The condensed droplets in the
valley are then evaporated due to the different equilibrium vapor pressure of
ice and water, resulting in a non-frost band on both hydrophobic and
superhydrophilic surfaces. The frost growth is systematically studied by
employing various levels of ambient humidity, surface wettability, and surface
geometry. Numerical simulations show the critical role of diffusion of water
vapor in the formation of the discontinuous frost pattern.
