Meltwater Evolution during Defrosting on Superhydrophobic Surfaces

Defrosting is essential
for removing frost from engineering surfaces, but some fundamental
issues are still unclear, especially for defrosting on superhydrophobic
surfaces. Here, defrosting experiments on prepared superhydrophobic
surfaces were conducted along with the investigation on meltwater
evolution characteristics. According to the experiments, the typical
meltwater evolution process on superhydrophobic surfaces can be divided
into two stages: dewetting by edge curling and dewetting by shrinkage.
The edge curling of a meltwater film is a distinct phenomenon and
has been first reported in this work. Profiting from the ultralow
adhesion of the superhydrophobic surface, edge curling is mainly attributed
to two unbalanced forces (one at the interface between the ice slurry
layer and pure water layer and the other in the triple phase line
area) acting on the layered meltwater film. During the multi-meltwater
evolution process, the nonbreaking of chained droplets on superhydrophobic
surfaces is also an interesting phenomenon, which is controlled by
the interaction between the surface tension and the retentive force
because of contact angle hysteresis. An approximate criterion was
then developed to explain and determine the status of chained droplets,
and experimental data from various surfaces have validated the effectiveness
of this criterion. This work may deepen the understanding of defrosting
on superhydrophobic surfaces and promote antifrosting/icing applications
in engineering.