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A novel microstirring strategy is applied to accelerate the digestion rate of the substrate -benzoyl--arginine-4-nitroanilide (-BAPA) catalyzed by sol-gel encapsulated trypsin. We use an ac nonlinear electrokineticvortexflow to stir the solution in a microfluidic reaction chamber to reduce the diffusion length between the immobilized enzyme and substrate in the solution. High-intensity nonlinear electroosmotic microvortices, with angular speeds in excess of 1 cm/s, are generated around a small conductive ion exchange granule when ac electric fields (133 V/cm) are applied across a miniature chamber smaller than . Coupling between these microvortices and the on-and-off electrophoretic motion of the granule in low frequency (0.1 Hz) ac fields produces chaotic stream lines to stir substrate molecules sufficiently. We demonstrate that, within a 5-min digestion period, the catalytic reaction rate of immobilized trypsin increases almost 30-fold with adequate reproducibility due to sufficient stirring action through the introduction of the nonlinear electrokineticvortices. In contrast, low-frequency ac electroosmotic flow without the granule, provides limited stirring action and increases the reaction rate approximately ninefold with barely acceptable reproducibility . Dye molecules are used to characterize the increases in solute diffusivity in the reaction reservoir in which sol-gel particles are placed, with and without the presence of granule, and compared with the static case. The solute diffusivity enhancement data show respective increases of and times, with and without the presence of granule. These numbers are consistent with the ratios of the enhanced reaction rate.


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