Nano- and microchannels are fabricated using a novel deposited column/void network silicon film as a sacrificial material. This nanostructured silicon consists of nanometer-sized columns defined normal to the substrate in a void matrix, where the voids are continuously connected with each other, forming a network. The void network structure results in a high sacrificial layer etch rate due to the void network-enhanced transport of reactant and reaction products during the etching process, and high effective surface area. The use of our unique deposited column/void network material coupled with lift-off processing results in a manufacturable process for nano- and microchannel and nano- and microcavity fabrication. The approach provides extremely flat surfaces without a chemical-mechanical polishing process, and allows for multiple layers of channel or cavity structures with crossovers.