Copper oxide nanostructured coatings, showing (a)–(d) the names of each nanostructure type, the solution chemistry and bath conditions used to fabricate them, and SEM images of each resulting coating at two magnifications. SEM images of two multiscale surfaces comprised of CuO nanostructures grown directly onto microchannel copper samples are shown for the (e) CuO-3 and (f) CuO-4 nanocoatings.