Superhydrophobic and self-cleaning materials have been
an extensive
topic of research owing to their corrosion resistance, antifouling,
and anti-icing properties. In the past, superhydrophobicity in aluminum
has been obtained by a variety of techniques involving etching by
sandblasting, chemical etching, boiling in water, etc. followed by
treatment with a fluorochemical and organic solution. However, these
techniques are not controlled, might not be easy to implement on a
large scale, and mostly make use of fluorochemicals, which are risky
for human health and the environment. Therefore, there is a need for
a rapid and controlled fabrication process that can provide patterned
superhydrophobicity without compromising the environment or the human
health. Here, a rapid, controlled, and environmentally friendly procedure
for fabricating a superhydrophobic and self-cleaning aluminum surface
has been developed, achieving a contact angle of 158.06° and
a sliding angle of 1.94°. In the two-step process, a rough surface
was obtained using the laser etching technique in under 3 min, which
resulted in a precisely controlled pattern with a dual-scale roughness
on the surface (∼20–30 μm). Finally, a low surface
energy was imparted to the surface by treatment with stearic acid
where a low concentration of 2 × 10–4 M and
no more than 10 s of exposure was found to be sufficient. Unlike various
superficially coated materials, this superhydrophobic surface is durable
and does not lose its properties after dipping in water for up to
4 days, encountering fine sand or mud, or at extreme surrounding temperatures
of −18 to 100 °C. Thus, this rapid and controlled process
for obtaining superhydrophobic aluminum potentially can be deployed
for large-scale, structural applications.