An array of nanowires having a relatively constant diameter and techniques and apparatus for fabrication thereof are described. In one embodiment, a technique for melting a material under vacuum and followed by pressure injection of the molten material into the pores of a porous substrate produces continuous nanowires. In another embodiment, a technique to systematically change the channel diameter and channel packing density of an anodic alumina substrate includes the steps of anodizing an aluminum substrate with an electrolyte to provide an anodic aluminum oxide film having a pore with a wall surface composition which is different than aluminum oxide and etching the pore wall surface with an acid to affect at least one of the surface properties of the pore wall and the pore wall composition.