A method is disclosed for fabricating free-standing polymeric nanopillars or nanotubes with remarkably high aspect ratios. The nanopillars and nanotubes may be used, for example, in integrated microfluidic systems for rapid, automated, high-capacity analysis or separation of complex protein mixtures or their enzyme digest products. One embodiment, preferably fabricated entirely from polymer substrates, comprises a cell lysis unit; a solid-phase extraction unit with free-standing, polymeric nanostructures; a multi-dimensional electrophoretic separation unit with high peak capacity; a solid-phase nanoreactor for the proteolytic digestion of isolated proteins; and a chromatographic unit for the separation of peptide fragments from the digestion of proteins. The nanopillars and nanotubes may also be used to increase surface area for reaction with a solid phase, for example, with immobilized enzymes or other catalysts within a microchannel, or as a solid support for capillary electrochromatography-based separations of proteins or peptides.