Surfaces with extreme wettability
(too low, superhydrophobic; too
high, superhydrophilic) have attracted considerable attention over
the past two decades. Titanium dioxide (TiO2) has been
one of the most popular components for generating superhydrophobic/hydrophilic
coatings. Combining TiO2 with ethanol and a commercial
fluoroacrylic copolymer dispersion, known as PMC, can produce coatings
with water contact angles approaching 170°. Another property
of interest for this specific TiO2 formulation is its photocatalytic
behavior, which causes the contact angle of water to be gradually
reduced with rising timed exposure to UV light. While this formulation
has been employed in many studies, there exists no quantitative guidance
to determine or tune the contact angle (and thus wettability) with
the composition of the coating and UV exposure time. In this article,
machine learning models are employed to predict the required UV exposure
time for any specified TiO2/PMC coating composition to
attain a certain wettability (UV-reduced contact angle). For that
purpose, eight different coating compositions were applied to glass
slides and exposed to UV light for different time intervals. The collected
contact-angle data was supplied to different regression models to
designate the best method to predict the required UV exposure time
for a prespecified wettability. Two types of machine learning models
were used: (1) parametric and (2) nonparametric. The results showed
a nonlinear behavior between the coating formulation and its contact
angle attained after timed UV exposure. Nonparametric methods showed
high accuracy and stability with general regression neural network
(GRNN) performing best with an accuracy of 0.971, 0.977, and 0.933
on the test, train, and unseen data set, respectively. The present
study not only provides quantitative guidance for producing coatings
of specified wettability, but also presents a generalized methodology
that could be employed for other functional coatings in technological
applications requiring precise fluid/surface interactions.