Superhydrophobic silicon fabricated by phosphomolybdic acid-assisted electrochemical etching

Controllable geometry silicon surfaces with superhydrophobicity are difficult to be fabricated without photolithography techniques. Superhydrophobic silicon surfaces with water contact angle larger than 150º and sliding angle less than 10º have been successfully fabricated by electrochemical etching strategy. Squarelike hole arrays with controllable geometries, especially ole width and depth were formed on silicon. Compared with the chemical composition, the obvious change of the hole size and surface roughness with etching time was actually the intrinsic factors for wetting regulation. The superhydrophobic silicon exhibited good stability even after storage in air and oil for 2 months. Moreover, the relatively stable superhydrophobic silicon exhibited good self-cleaning and water-proofing properties in air and oil.