Porous anodic aluminum oxide (AAO) films have been widely used by researchers as templates for growing arrays of nanowires because their pores comprise self-aligned nanochannels with extremely high aspect ratios. [1][2][3][4][5][6][7] Furthermore, the nanochannels can be laterally self-organized into domains of hexagonally closed-packed (hcp) ordered arrays under certain anodization conditions. [8,9] The use of lithographic guiding techniques such as stamp nanoimprinting, [10] focused ion beam (FIB) sputtering, [11] and laser holographic printing [12] has extended the number of nanochannels selforganized within a single ordered domain from merely 10 2 to a tremendous number of 10 10 . Hereafter, single-domain ideally ordered nanochannel arrays fabricated by lithographic guiding techniques are referred to simply as ordered arrays for simplicity.[13] The availability of large ordered nanochannel arrays has inspired researchers around the world to design and fabricate nanocomposites and nanodevices based on AAO templates. [4,14] One of the key steps towards the realization of the full potential of these exciting nanomaterials and better exploitation of the features of these AAO templates is to develop techniques for growing different materials in different regions of an ordered array. In previous work, a method for fabricating custom-designed arrays of nanochannels by selectively closing specific regions of the nanochannels using FIB bombardment has been reported. [15] This method facilitates the selective growth of materials within open nanochannels, enabling the creation of a nanocomposite comprising arrays of filled and empty nanochannels. In order to take full advantage of the potential of AAO templates, the ideal situation would involve filling different regions of an array with different materials. One conceptually simple and elegant method to achieve this desired objective is to open the closed nanochannels again and grow a second material into these reopened channels. Here, we report the development of a complete resist-free lithographic process for the selective closing and reopening of AAO nanochannels using FIB direct writing. We also demonstrate the potential of this method by fabricating arrays of Ag/Cu nanowires arranged in various custom-designed geometries.The ordered nanochannel arrays used in our experiments have been prepared by a FIB lithographic guiding process, as described previously in the literature.[16] The exposure of an ordered nanochannel to a Ga FIB with different beam energies results in the formation of different surface morphologies. For example, upon exposure to a flux of 2.0 Â 10 16 cm À2 30 keV ions, the pores of the nanochannels have been significantly reduced in size, as clearly shown by the right panel of Figure 1a. This figure shows a field-emission scanning electron microscopy (SEM, JEOL 6700) image of the boundary between a pristine (left) and bombarded region (right). Pore size distributions of arrays exposed to different FIB doses have been obtained by processing SEM image...