Microfabricated electrophoretic separation devices have been produced by an injection-molding process. The strategy for producing the devices involved solution-phase etching of a master template on a silicon wafer, followed by electroforming more durable injection-molding masters in nickel from the silicon master. One of the nickel electroforms was then used to prepare an injection mold insert, from which microchannel chips in an acrylic substrate were mass-produced. The microchannel devices were used to demonstrate high-resolution separations of double-stranded DNA fragments with total run times of less than 3 min. Run-to-run and chip-to-chip reproducibility was good, with relative standard deviation values below 1% for the run-to-run data and in the range of 2-3% for the chip-to-chip comparisons. Such devices could lead to the production of low-cost, single-use electrophoretic chips suitable for a variety of separation applications, including DNA sizing, DNA sequencing, random primary library screening, and rapid immunoassay testing.

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A flat electrophoretic migration velocity profile Is assumed to be characteristic of current capillary zone electrophoresis (CZE) separations. However, this electrophoretic velocity profile may not actually exist In some experiments due to heat generated within the capillary. The actual migration velocity stream within capillary electrophoresis tubes probably has a parabolic profile. Using a parabolic model, we have developed an expression that quantitatively relates the plate height to experimental parameters. The plate height In CZE is a strong function of the capillary radius, the strength of the applied field, and the buffer concentration. The newly derived plate height equation suggests the following: (a) large operating voltages may broaden solute peaks; (b) capillaries should be carefully thermostated; (c) thermostating at elevated temperatures may lead to Improved plate heights; and (d) decreasing the electrolyte concentration In the buffer allows the use of wider capillaries. Wider capillaries, In turn, would permit more convenient operation and large sample volumes.

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