  Hydrophobic (HPo) surfaces for atmospheric water harvesting applications
require sophisticated wettability and microstructure patterns, which suffer
from high cost and low durability against severe mechanical and environmental
degradations. Inspired by the leaves of Welwitschia mirabilis, a long lifespan
desert-living plant, we present a robust superhydrophilic (SHPi) surface design
which is capable of enhancing both dew condensation and fog capture. The
surface consists of a parallel-aligned millimetric wavy topography on top of
which random nanostructures are grown. By studying the liquid dynamics, we have
shown a unique mechanism of water transport on the SHPi wavy surface by droplet
splitting and Laplace pressure gradient. It has been revealed that the
efficient water transport on the SHPi wavy surface synergistically interacts
with the enhanced diffusion flux of water vapor on the convex regions and
significantly improves the efficiency of filmwise condensation. We have further
demonstrated that wavy features enhance the probability of fog droplet
collisions by disturbing the air flow and increasing the mean free path of fog
droplets.
