Topographic structures and chromatographic supports in microfluidic separation devices

A review is given of the literature on the design, development and use of micromachined devices for separations in the liquid phase. The emphasis is on those devices that offer more than just an empty channel for, e.g., electrophoretic separation. Topographic structures have been incorporated in the channels during their microfabrication, offering a variety of possibilities for the separation of (mainly) DNA molecules based on different principles. Supports for a stationary phase for chromatographic separations have been introduced in the channels in different ways: by packing of the channels with stationary phase particles, by polymerization of monolithic structures, or by lithographic machining of pillars in the channels. It is shown that the latter strategy gives the highest potential for increasing the separation power of the devices. Still, more conventional approaches are closer to a routine application.