  The wetting and filling properties of a fluid adsorbed on a solid grooved
substrate are studied by means of a microscopic density functional theory. The
grooved substrates are modelled using a solid slab, interacting with the fluid
particles via long-range dispersion forces, to which a one-dimensional array of
infinitely long rectangular grooves is sculpted. By investigating the effect of
the groove periodicity and the width of the grooves and the ridges, a rich
variety of different wetting morphologies is found. In particular, we show that
for a saturated ambient gas, the adsorbent can occur in one of four wetting
states characterised by i) empty grooves, ii) filled grooves, iii) a formation
of mesoscopic hemispherical caps iv) a macroscopically wet surface. The
character of the transition between particular regimes, that also extend
off-coexistence, sensitively depends on the model geometry. A temperature at
which the system becomes completely wet is considerably higher than that for a
flat wall.
