Fluidics microchip interface

Sanders, J.C., Breadmore, M.C., Mitchell, P.S., Landers, J.P., A simple PDMS-based electro-fluidic interface for microchip electrophoretic separations. Analyst 2002, 127, 1558-1563. 

Figure 5-10 Detection system for LIF detection on microchips. Fluidic and electrical interfaces are indirectly fundamental to the detection system.The fluidic interface drives the preparation and flushing of the chip preseparation and postseparation, while the electrical interface drives the electrophoretic separation and controls the flow of fluid through the chip architecture via electrokinetic valving.

Fig. 9.7.13 Early fluidic interface to microchip designed by the author using an o-ring sealing system. Details show o-ring mating with fluid ports on chip, which is pressed to o-rings using an acrylic cover plate that is bolted to support block underneath. The chip mount is made from transparent acrylic for demonstration purposes.

LIF detection is the most sensitive optical method so far, but is hard to miniaturize in order to satisfy the ultimate goal of a microfluidic chip that assembles all analytical processes within one micrometerscale microstructure. Therefore, how to achieve the miniaturization of fluorescence detection on microdevices is becoming an active field for lab-on-a-chip research. Several examples demonstrate recent advances in miniaturized LIF detection on the microchip. In 2005, Renzi et al. designed a hand-held microchip-based analytical instrument that combines fluidic, optics, electrical power, and interface modules and integrates the functions of fluidics, microseparation, lasers, power supplies etc., into an... 

Finally, the dead volumes developed when capillary coimections and other junctions to the fluidic chip to provide off-chip processing, such as the interface to MS, can significantly degrade separation performance and introduce sample carryover or sample loss. For example, Gao and coworkers [124] estimated 4 pF for the dead volume associated with their miniaturized trypsin membrane reactor. As noted above, the typical peak volume associated with microchip electrophoresis is on the order of 10 pF, which demands that nearly all protein processing post-separation be done directly on-chip so as not to degrade separation... 

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