Ultrafast Self-Healing Superhydrophobic Surface for Underwater Drag Reduction

The self-healing superhydrophobic surfaces have attracted
great
interest owing to restoring superhydrophobicity without preparation
crafts. However, the self-healing superhydrophobic surface still faces
the dilemma of long repairing time. Especially in aqueous environments,
superhydrophobic surfaces are highly susceptible to contamination
and damage. In the current study, a superhydrophobic surface with
ultrafast repairability was developed, which apply for drag reduction
in aqueous medium. The prepared superhydrophobic surface can recover
superhydrophobicity in only 30 s after severe physical and chemical
damage. In addition, this research pioneered the combination of superhydrophobicity
and porous structures for underwater drag reduction. The study of
drag reduction confirms that the superhydrophobic surface can reduce
the frictional drag by about 43% in the water. However, the drag reduction
rate of the superhydrophobic surface with the porous structure can
be improved to 76% due to increased stability of the air layer. More
importantly, the porous structure with the average pore size of 50
μm has the most excellent stability through further experiments
on the underwater air layer. This is attributed to the proper size
of the pore to effectively balance the capillary force and resist
wetting in the marginal region. This study will bring inspiration
for the large-scale application of superhydrophobic surfaces and long-term
drag reduction.