Microfabricated valves

Several review articles describing miniaturized devices for fluid handling have been published that give excellent and detailed overviews of the state of the art [3,4]. Here, some examples of microfabricated valves and pumps will be given to illustrate the possibilities of silicon microtechnology. 

The ability to fill a device with many different fluids in different channels and chambers allows for the implementation of a simple and robust geometric method of metering solutions. The principle behind this scheme is to set up a geometry in which two microfluidic chambers may be primed with different solutions and connected via a fluidic interface that is controlled by a microfabricated valve (Fig. 11.4). With a central interface valve closed, the two chambers are first deadend filled with two different solutions using the POP technique. Once both chambers have been completely filled, containment valves are actuated, isolating the chambers from the rest of the chip. The interface valve is then opened, creating a... 

M.A. Uuger, H.P. Chou, T. Thorseu, A. Scherer, aud S.R. Quake, Mouolithic microfabricated valves aud pumps by multilayer soft lithography, Scieuce, 288, 113-116, (2000). 

M. A. Unger, H.-P. Chou, T. Thorsen, A. Scherer and S. R. Quake, Monolithic microfabricated valves and pumps by multilayer soft hthography. Science, 288 (2000), 113-116. 

Unger MA, Chou HP, Thorsen T, Scherer A, Quake SR (2000) Monolithic microfabricated valves and pumps by multilayer soft lithography. Science 288 113-116... 

A microfabricated valve with a sample loop, actuated by an electromagnet, is used in some portable GC instruments (7). Usually these instruments use a microfabricated thermal conductivity detector and a microbore column. The use of this approach, however, is limited, since the volume of injected vapor can be changed only by changing the volume of the sample loop. 

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