Abstract: Fabrication techniques for forming arbitrarily shaped fluid capillaries at dimensions below 1 &mgr;m and for forming optical waveguides in the same devices with the same fabrication processes include methods to make integral optical waveguide/fluid-flow systems for greater miniaturization, integration and parallelism of optical excitation and detection systems for the sampling of small volumes. Capillaries with widths below 1 &mgr;m dimensions are fabricated using photolithography and reactive ion etching on glass substrates or by provision of a sacrificial layer, having the configuration desired for a microchannel, covered by a high refractive index material in which a waveguide is formed. Removal of the sacrificial layer produces a microchannel aligned with the waveguide. Dye labeled DNA molecules are driven electrophoretically through the micrometer size channels light emission from and individual molecules can be observed.