Organic-aqueous (phenol) liquid extraction is one of the commonly used DNA purification methods. Effective mass transfer of biological material between the discrete fluid phases is key to achieving efficient extraction when designing microfluidic devices based on this technique. In the microscale regime, mass transfer is often diffusion limited. However, mass transfer can be enhanced through the formation of discrete droplets within a microchannel, which leads to a recirculation flow pattern within the droplet. This recirculation increases the mass transfer rate of material to the organic-aqueous interface. In this study, an experimental and computational examination of sample extraction between the organic and aqueous phases through droplet formation is presented. The experiment is conducted within a converging dual inlet microfluidic channel fabricated in PDMS. By controlling the capillary number of the flow, different flow patterns are created in the channel. The flow patterns are examined using a computational fluid dynamics (CFD) simulation. The CFD model successfully simulates the flow behavior under a variety of flow conditions and provides a closer examination of the internal recirculation pattern within the droplet. The experimental sample extraction utilizes a fluorescent dye localization technique and shows that the droplet flow offers a significant improvement in the speed of sample extraction over diffusional mixing. A preliminary test demonstrates the feasibility of using the droplet formation for fast extraction with biological samples.
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