Counter-current arrangement of microfluidic liquid-liquid droplet flow contactors

Abstract

The objective of microfluidic droplet flow is the control and manipulation of fluids on the sub-mm scale. This article describes the microfluidic droplet flow in a liquid-liquid contacting unit utilizing microchannels and millichannels and their counter-current arrangement. A contacting module consists of a droplet generator, a channel to enable an intensified mass transfer between two fluids and a liquid-liquid separation device. Experiments were performed with deionized water as a continuous phase and various organic solvents as a dispersed phase. The organic droplets are generated by direct coflowing injection through a needle located in the center of the microchannel. Droplet generation and flow patterns were optically investigated in straight and winding channels. The adjacent separation unit continuously splits the organic, dispersed phase. The combined effects of gravity, wetting characteristics of the wall material and capillary forces nearly completely separate the two fluids over a wide range of flow rates. Based on the mixer-settler system, a microfluidic extraction unit is proposed that enables a multistage counter-current arrangement.