Condensation on Superhydrophobic
Surfaces: The Role
of Local Energy Barriers and Structure Length Scale
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Abstract
Water condensation on surfaces is a ubiquitous phase-change
process
that plays a crucial role in nature and across a range of industrial
applications, including energy production, desalination, and environmental
control. Nanotechnology has created opportunities to manipulate this
process through the precise control of surface structure and chemistry,
thus enabling the biomimicry of natural surfaces, such as the leaves
of certain plant species, to realize superhydrophobic condensation.
However, this “bottom-up” wetting process is inadequately
described using typical global thermodynamic analyses and remains
poorly understood. In this work, we elucidate, through imaging experiments
on surfaces with structure length scales ranging from 100 nm to 10
μm and wetting physics, how local energy barriers are essential
to understand non-equilibrium condensed droplet morphologies and demonstrate
that overcoming these barriers via nucleation-mediated droplet–droplet
interactions leads to the emergence of wetting states not predicted
by scale-invariant global thermodynamic analysis. This mechanistic
understanding offers insight into the role of surface-structure length
scale, provides a quantitative basis for designing surfaces optimized
for condensation in engineered systems, and promises insight into
ice formation on surfaces that initiates with the condensation of
subcooled water