An article, at least one surface of which is operative in that it is provided with a plurality of microscopic discrete depressions which, in use, are repeatedly filled with a volume of liquid which is subsequently transferred as a result of contact with another article, said article being coated with a layer of a ceramic material providing the operative, liquid-receiving surface of the article, wherein the shape of the depressions is essentially closed, said depressions being - defined around their peripheries by a substantially or predominantly continuous wall structure comprised of the material of which the article surface is constituted, - of a cross-sectional shape which is symmetrical about one or both of a lateral and a medial axis perpendicular thereto or is of a cross-sectional shape which can sheared about its mid-point to give such a shape, those portions of the continuous wall structure defining the depression and being disposed on either side of such axes being the medial and lateral side walls of the depression respectively, - arranged adjacent one another to form a substantially uniform pattern of depressions over the operative surface of the article such that any two adjacent depressions share a portion of the wall structure which at least partially defines them, wherein each of at least one of the pairs of lateral or medial sidewalls are contoured, the contourof one of the pair being generally the mirror image of the other so that together, said sidewalls define - at least one constriction internally of the depression where each of the sidewalls in that pair is most proximate the other, and - at least two adjacent depression portions on either side of said constriction and having a maximum lateral or medial dimension greater than the lateral or medial dimension of the constriction such that fluid flow from one portion to the other is partially restricted by said constriction. - defined around their peripheries by a substantially or predominantly continuous wall structure comprised of the material of which the article surface is constituted, - of a cross-sectional shape which is symmetrical about one or both of a lateral and a medial axis perpendicular thereto or is of a cross-sectional shape which can sheared about its mid-point to give such a shape, those portions of the continuous wall structure defining the depression and being disposed on either side of such axes being the medial and lateral side walls of the depression respectively, - arranged adjacent one another to form a substantially uniform pattern of depressions over the operative surface of the article such that any two adjacent depressions share a portion of the wall structure which at least partially defines them, wherein each of at least one of the pairs of lateral or medial sidewalls are contoured, the contourof one of the pair being generally the mirror image of the other so that together, said sidewalls define - at least one constriction internally of the depression where each of the sidewalls in that pair is most proximate the other, and - at least two adjacent depression portions on either side of said constriction and having a maximum lateral or medial dimension greater than the lateral or medial dimension of the constriction such that fluid flow from one portion to the other is partially restricted by said constriction.