  Superhydrophobic surfaces with the self-cleaning behavior of lotus leaves are
sought for drag reduction and phase change heat transfer applications. These
superrepellent surfaces have traditionally been fabricated by random or
deterministic texturing of a hydrophobic material. Recently, superrepellent
surfaces have also been made from hydrophilic materials, by deterministic
texturing using photolithography, without low-surface energy coating. Here, we
show that hydrophilic materials can also be made superrepellent to water by
chemical texturing, a stochastic rather than deterministic process. These
metallic surfaces are the first analog of lotus leaves, in terms of
wettability, texture and repellency. A mechanistic model is also proposed to
describe the influence of multiple tiers of roughness on wettability and
repellency. This demonstrated ability to make hydrophilic materials
superrepellent without deterministic structuring or additional coatings opens
the way to large scale and robust manufacturing of superrepellent surfaces.
