  Bumps are omnipresent from human skin to the geological structures on
planets, which offer distinct advantages in numerous phenomena including
structural color, drag reduction, and extreme wettability. Although the
topographical parameters of bumps such as radius of curvature of convex regions
significantly influence various phenomena including anti-reflective structures
and contact time of impacting droplets, the effect of the detailed bump
topography on growth and transport of condensates have not been clearly
understood. Inspired by the millimetric bumps of the Namib Desert beetle, here
we report the identified role of radius of curvature and width of bumps with
homogeneous surface wettability in growth rate, coalescence and transport of
water droplets. Further rational design of asymmetric convex topography and
synergetic combination with slippery coating simultaneously enable
self-transport, leading to unseen five-fold higher growth rate and an order of
magnitude faster shedding time of droplets compared to superhydrophobic
surfaces. We envision that our fundamental understanding and innovative design
of bumps can be applied to lead enhanced performance in various phase change
applications including water harvesting.
