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What you're seeing in this video is a highly magnified view
of water droplet condensation on a cool nanostructured
surface, kind of like dew formation on a cool spring morning
The surface is special in that it consists of an array
of very small silicon nanopillars, which are spaced
two microns apart, are six microns tall, and are
zero point three microns thick, or about
three hundred times thinner than human hair.
The pillars are chemically coated to be hydrophobic,
which means water-hating. This allows the growing droplets
to merge and easily jump from the surface, which results
in much more efficient heat transfer.
If you look closely, you'll notice that some droplets
are very round, and some are balloon-shaped, with
a stretched neck at the bottom. The round ones
form and grow on the tips of pillars, while the
ballon shapes grow from inside the pillared array.
What we're studying is the growth difference between
these two droplet types: the faster droplets grow, the more
heat they can carry away before jumping, which is
actually very important for many industrial applications,
such as steam power plant condensers,
evaporation-based desalination plants, and
solar collectors. Our findings show that contrary to
previous intuition, these ballon-shaped droplets are
highly favorable for efficient condensation, since they
grow six times faster than drops sitting on the pillar tops.
In the future, we plan to leverage this new information
to create highly efficient, scalable condensing surfaces.