Microfabricated fluidic devices valves

An integrated microfabricated cell sorter has been constructed using a control layer and a fluidic layer fabricated on PDMS [890]. The control layer consists of valves that will be pneumatically controlled by pressurized N2. This device is superior to an electrokinetic sorter, which suffers from buffer incompatibilities and frequent voltage adjustments because of ion depletion or pressure imbalance due to evaporation. E. coli cells expressing EGFP were sorted and selected out from a cell mixture which also contained E. coli cells expressing the / -nitrobenzyl (PNB) esterase. About 480,000 cells have been sorted at a rate of 44 cefls/s in 3 h. The recovery yield was 40% and the enrichment ratio was about 83-fold [890]. 

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... 

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