Evaporation is crucial in many applications. One of the
critical
parameters affecting evaporation is surface wettability, which is
often tailored using coatings and micro- or nanoscale features on
the surface. While this approach has advanced many technologies, the
ability to control wettability dynamically can add new functionalities
and capabilities that were not possible before. This study demonstrates
how a self-cleaning superhydrophobic surface with an equilibrium contact
angle of 155° can dynamically change to a superhydrophilic surface
with a contact angle near 0°, resulting in drastically different
evaporation characteristics. Specifically, we find that the evaporation
rate and surface temperature reduction due to the resulting cooling
are 3 times higher due to the change in surface wettability. This
change in wetting behavior is due to the use of an amino-silane [N-(2-aminoethyl)-11-aminoundecyltrimethoxysilane]-functionalized
surface, which is altered in the presence of dilute acetic acid. Upon
complete evaporation, the surface reverts to superhydrophobic behavior.
This reversible behavior is not seen in traditional nonwetting coatings
like perfluorodecyltrichlorosilane and lauric acid. This strategy
for dynamic control of wettability and evaporation can lead to advancements
in many applications ranging from self-assembly-based fabrication
processes to oil–water separation and advanced thermal management
technologies.