The invention relates to an article of manufacture which includes a substrate, and on at least one surface thereof, a porous coating which has a total thickness in the range of up to about 50 microns and which consists of a plurality of discrete adjacent strata, wherein each discrete stratum is porous, inclusive of porous interfaces, and is fabricated from at least one substance selected from the group consisting of metals and metal oxides. The article is made by vaporizing a metal under vacuum conditions, optionally in an oxidizing atmosphere, at predetermined intervals of time, such that a deposit of a desired total thickness is formed on the substrate as a coating consisting of a plurality of discrete adjacent strata.