  Inspired by the stenocara beetle, we study an ideal flat surface composed of
a regular array of hydrophilic circular patches in a hydrophobic matrix on an
incline of tilt $\alpha$ with respect to the horizontal. Based on an exact
solution of the Laplace-Young equation at first order in the Bond number, the
liquid storage capacity of the surface is maximized as function of the patch
radius, for suitable ranges of hydrophilic and hydrophobic contact angles, for
tilt angles such as $45^{\circ}$ or $90^\circ$. It is found that the optimal
radius equally prevents dewetting from the top of the patches and overflow at
the bottom. These theoretical considerations are validated by several
experiments for the glass/octadecyltrichlorosilane (OTS) system involving
different patch sizes and different inclinations. In a simple dynamical model,
taking into account the flux of fog onto the surface or condensation on a
suitably cooled surface, we find that the conditions for maximum harvest agree
with the ones of maximum static storage. The method could be developed for drop
storage and drop transport applications such as water-harvesting systems.
