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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number of gauche bonds into a highly ordered lattice will disrupt the lattice disproportionally, so that the number of "disordered" methylenes [m*] will be significantly larger than the number of gauche bonds [/«(g)]. The ratio of the number of "disordered" methylenes to the number of gauche bonds (minus the background contribution), that is m*/[m{g) -0.1], evaluated at a temperature just above Ta, is in the range 3.0-4.5 for C17, C25, and C36. This ratio varies for C50 and C60 because m(g) changes with temperature. However, near the high-temperature end of temperature region II, the ratio is around 4.5 for these chains.Temperature Region III. This narrow temperature region, in which actual melting occurs, was discussed in the Results section.In summary, it appears that the melting behavior of the «-alkanes examined here may be quite similar. Evidence to that effect is our observation that at a temperature 0.85 ± 0.45°below the melting point, the degree of disorder as measured by the number of gauche bonds per chain is nearly the same for C17. C25, C36, C50, and C60 (see Table I). This suggests that in this temperature region the disorder in the chain ends is quantitatively similar for the different crystalline «-alkanes.Acknowledgment. We gratefully thank the National Science Foundation (DMR 87-01586) and the National Institutes of Health (GM 27690) for supporting this work. We also thank Professor Leo Mandelkern for valuable discussions and encouragement during the course of this project.

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