Field-Effect Flow Control

FIGURE 3.15 Differential EOF pumping rates were achieved from different gate voltages applied to the field-effect flow control electrodes. This produced (a) positive pressure for flow down and (b) negative pressure for flow up the field-free microchannel (ft) [371]. Reprinted with permission from the American Chemical Society. 

Sniadecki, N.J., Lee, C.S., Sivanesan, P., DeVoe, D.L., Induced pressure pumping in polymer microchannels via field-effect flow control. Anal. Chem. 2004, 76, 1942-1947. 

Schasfoort, R. B.M., Schlautmann, S., Hendrikse, J., van den Berg, A., Field-effect flow control for microfabricated fluidic networks. Science 1999, 286(5441), 942-945. 

Field-effect flow control Flow field-effect transistor Fluidic amphflcation and oscillation Fluidic logic... 

Schasfoort RBM, Schlautmaim S, Hendrikse J, van den Berg A (1999) Field-effect flow control for microfabricated networks. Science 286 942-945... 

Flow field-effect transistor Field-effect flow control Fluerics Fluidic logic Fluidic amplification and oscillation... 

The invention of the germanium transistor in 1947 [I, 2] marked the birth of modem microelectronics, a revolution that has profoundly influenced our current way of life. This early device was actually a bipolar transistor, a structure that is mainly used nowadays in amplifiers. However, logical circuits, and particularly microprocessors, preferentially use field-effect transistors (FETs), the concept of which was first proposed by Lilicnficld in 1930 [3], but was not used as a practical application until 1960 [4]. In a FET, the current flowing between two electrodes is controlled by the voltage applied to a third electrode. This operating mode recalls that of the vacuum triode, which was the building block of earlier radio and TV sets, and of the first electronic computers. 

Aquatic ecotoxicology evaluates the probability of an adverse impact of a substance on the aquatic environment at the present as well as in the future, considering the total flow into the system (Klein, 1999). It encompasses laboratory ecotoxicity tests on appropriate test organisms to explore relationships between exposure and effect under controlled conditions as well as studies of the effects of substances or effluents under a variety of ecological conditions in complex field ecosystems (Chapman, 1995). 

Because of the various effects noted above, the entire subject of heat transfer to fluids without phase change is complex and in practice is treated as a series of special cases rather than as a general theory. All cases considered in this chapter do, however, have a phenomenon in common in all of them the formation of a thermal boundary layer, analogous to the hydrodynamic Prandtl boundary layer described in Chap. 3, takes place it profoundly influences the temperature field and so controls the rate of heat flow. 

Experience from many conventional oil and gas fields has shown that solids control should be installed before solids production occurs. It generally becomes more difficult to control further solids flow as the cumulative volume of produced solids increases. Consequently, in conventional oil and gas fields, initial solids control installations have proven to be consistently more successful than remedial treatments. Future enhancements will certainly improve the success of remedial treatments. The technology is continually advancing, and cost-effective through-tubing remedial methods are now available (55). 

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