Frequency dependent multiphase flows on centrifugal microfluidics†
The simultaneous flow of gas and liquids in large scale conduits is an established approach to enhance the performance of different working systems under critical conditions. On the microscale, the use of gas–liquid flows is challenging due to the dominance of surface tension forces. Here, we present a technique to generate common gas–liquid flows on a centrifugal microfluidic platform. It consists of a spiral microchannel and specific micro features that allow for temporal and local control of stratified and slug flow regimes. We investigate several critical parameters that induce different gas–liquid flows and cause the transition between stratified and slug flows. We have analytically derived formulations that are compared with our experimental results to deliver a general guideline for designing specific gas–liquid flows. As an application of the gas–liquid flows in enhancing microfluidic systems' performance, we show the acceleration of the cell growth of E. coli bacteria in comparison to traditional culturing methods.