Optimization of turn geometries for microchip electrophoresis

Chip-based microcolumn separation systems often require serpentine channels to achieve longer separation lengths within a compact are;a. However, anal yte bands traveling through curved channels experience an increased dispers ion that can reduce the benefit of increased channel length. This paper pre sents analytical solutions for dispersions, numerical models for minimizing dispersion in microchannel turns, and experiments used to validate numeric al models and to demonstrate the effectiveness of dispersion-reduction sche mes. An analytical solution for the geometric dispersion caused by a consta nt radius turn is presented. We also propose metrics for characterizing the performance of miniaturized electrophoresis systems that utilize dispersio n-introducing turns. The analytical solution and metrics can be used to det ermine when compensating turns should be used and when these turns are eith er not necessary or ineffective. For situations where a constant radius tur n introduces significant geometric dispersion, numerical shape optimization routines were used to determine optimal geometries that minimize geometric dispersion while limiting reductions in channel width. Experiments using p hotobleached-fluorescence and caged-fluorescence visualization were conduct ed to validate the employed numerical models and to verify the turn designs proposed here.