Enhanced bioreaction efficiency of a microfluidic mixer toward high-throughput and low-cost bioassays

Microscale bioreactors are an important tool in performing bioassays. The speed and efficiency of these devices is often limited by the rate of reagent mixing. In spite of the various micromixing approaches, the coupled mixing/reaction process has yet to be clearly understood. This article presents experimental and computational studies on the enhancement of bioreaction rates using a novel cilia reactor. In the experiments, a biotin-avidin assay and a DNA hybridization assay were conducted to show the benefit of a cilia bioreactor compared with a simple diffusion reactor. A cilia reactor showed a shorter reaction time for approaching equilibrium. A numerical computation examined the bioreaction rate of the cilia reactor compared with the diffusion for (1) a biotin-avidin assay, (2) an immunoassay, and (3) a DNA hybridization assay. The reaction rate was characterized for each assay using the Damk?hler number (Da). When Da was greater than 10², the ratio of reaction time for the diffusion to cilia reactors linearly increased with Da, which could also save reagent usage by lowering the concentration of reagent probes. However, when the system had a Da smaller than 10², the reaction time of a cilia reactor could not be shortened because the assay was dominated by reaction rather than fluid mixing. The results offer a general approach for enhancing bioreaction rates by employing microfluidic mixers for a bioassay.