An evaluation of a real-time passive micromixer to the performance of a continuous flow type microfluidic reactor

Microfluidics has been developed as an important platform for biochemical/chemical reactions. How to enhance the performance of a microfluidic chemical reactor is one of the core concerns when designing the microfluidic device. In the pressure-driven microfluidics without micromixer, parabolic flow profile dominates the behaviors of the laminar flow as well as the reaction particles such as DNA fragments, proteins, and enzymes. The aim of this study is to elucidate and answer a question: does a groove-shape passive micromixer improve the performance of a continuous flow type microfluidic reactor? Two mold inserts were micro-milled in the experiments, one had regular microchannels and the other one had regular microchannels with groove-shape passive micromixers, and both polymeric chips were manufactured with hot embossing techniques. Multiple experiments were realized on both chips to evaluate the groove-shape passive mixer to the performance of a continuous flow type microfluidic reactor. Polymerase chain reaction (PCR) is a typical example of chemical reaction in microfluidics, a 99 bp DNA fragment from lambda-DNA was used as the target in the experiments. In this study, multiple experiments were carried out, analyzed, and concluded that the groove-shape passive mixing is not beneficial to the performance of a continuous flow type microfluidic reactor. The results showed that a regular microfluidic device without mixing had better amplification efficiency of the target DNA fragments, which indicated that using a real-time passive mixing component inside a continuous flow environment, increasing the chance of protein absorption and strengthening shear force to molecules, might cause the negative impact to the PCR reaction performance.