Miniaturization electroosmotic valves

Electroosmotic flow (EOE) is thus the mechanism by which liquids are moved from one end of the sepai ation capillai y to the other, obviating the need for mechanical pumps and valves. This makes this technique very amenable to miniaturization, as it is fai simpler to make an electrical contact to a chip via a wire immersed in a reservoir than to make a robust connection to a pump. More important, however, is that all the basic fluidic manipulations that a chemist requires for microchip electrophoresis, or any other liquid handling for that matter, have been adapted to electrokinetic microfluidic chips. 

There are still signiflcant technical hurdles that must be overcome for microchips to develop into an accepted and widespread technique. The unreliability of electroosmotic pumping and other microfluidic processes contributes to the lack of robustness of these systems. The miniaturization and integration of other components, such as pumps, valves, and detection schemes, onto the chip is another essential step for future development. The reader is referred to the reviews cited in the references for research performed with microchips [46-48]. 

Microchip technology (see Ref. 454 and Fig. 17) is revolutionizing chemical and biochemical testing. The microchip processes fluid rather than electrons. Both electrophoretic and electroosmotic techniques are used to pump the fluid. Pumps, valves, volume-measuring devices, and separation systems are on the microchip s surface. Microchip separation procedures include electrophoresis, chromatography and solid-phase biochemistry. Microchips allow true parallelism, miniaturization, multiplexing, and automation, and these key features provide a set of performance specifications that cannot be achieved with earlier technologies (64-68,454-463). 

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