Parallel separation of multiple samples with negative pressure sample injection on a 3-D microfluidic array chip

A simple and powerful microfluidic array chip-based electrophoresis system, which is composed of a 3-D microfluidic array chip, a microvacuum pump-based negative pressure sampling device, a high-voltage supply and an LIF detector, was developed. The 3-D microfluidic array chip was fabricated with three glass plates, in which a common sample waste bus (SWbus) was etched in the bottom layer plate to avoid intersecting with the separation channel array. The negative pressure sampling device consists of a microvacuum air pump, a buffer vessel, a 3-way electromagnet valve, and a vacuum gauge. In the sample loading step, all the six samples and buffer solutions were drawn from their reservoirs across the injection intersections through the SWbus toward the common sample waste reservoir (SWT) by negative pressure. Only 0.5 s was required to obtain six pinched sample plugs at the channel crossings. By switching the three-way electromagnetic valve to release the vacuum in the reservoir SWT, six sample plugs were simultaneously injected into the separation channels by EOF and electrophoretic separation was activated. Parallel separations of different analytes are presented on the 3-D array chip by using the newly developed sampling device.