We demonstrate the possibility to generate ultra-rapid, low-axial dispersion flows through flat-rectangular nano-channels, i.e., channels with a thickness as small as 100 nm. This is achieved by resorting to the very basic, yet often overlooked shear-driven flow principle. With the recent improvements in micro-channel manufacturing possibilities, the major advantage of this flow type, i.e., the possibility to impose quasi unlimitedly large flow velocities through sub-micron thin channels without running into conflict with Posiseuille's pressure-drop law, can now be fully exploited. Demonstrating the possibility to generate rapid tracer flows with Bodenstein numbers of over 100,000, the present study proves the practical feasibility of this novel micro-channel concept. As it opens the road towards an unprecedented range of short radial diffusion times, the system has potential applications in the conduction of ultra-rapid chromatographic separations, the conduction of short time-scale binding and reaction kinetics measurements in diffusion-free conditions, and the conduction of combinatorial drug and catalyst screening at unprecedented throughput frequencies. (C) 2004 Published by Elsevier Ltd.