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 characterized 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. The temperature at which the system becomes completely wet is considerably higher than that for a flat wall.

E Hála Laboratory of Thermodynamics Institute of Chemical Process Fundamentals Academy of Sciences 16502 Prague 6 Czech Republic Department of Physical Chemistry Institute of Chemical Technology Prague 166 28 Praha 6 Czech Republic

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