Factors Affecting the Spontaneous Motion of Condensate Drops on Superhydrophobic Copper Surfaces-FENG Jie

The coalescence-induced condensate drop motion on some
superhydrophobic surfaces (SHSs) has attracted increasing attention because of
its potential applications in sustained dropwise condensation, water collection,
anti-icing, and anticorrosion. However, an investigation of the mechanism of such
self-propelled motion including the factors for designing such SHSs is still limited.
In this article, we fabricated a series of superhydrophobic copper surfaces with
nanoribbon structures using wet chemical oxidation followed by fluorization
treatment. We then systematically studied the influence of surface roughness and
the chemical properties of as-prepared surfaces on the spontaneous motion of
condensate drops. We quantified the “frequency” of the condensate drop motion
based on microscopic sequential images and showed that the trend of this
frequency varied with the nanoribbon structure and extent of fluorination. More
obvious spontaneous condensate drop motion was observed on surfaces with a
higher extent of fluorization and nanostructures possessing sufficiently narrow spacing and higher perpendicularity. We attribute
this enhanced drop mobility to the stable Cassie state of condensate drops in the dynamic dropwise condensation process that is
determined by the nanoscale morphology and local surface energy.

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