(248e) Stability, Oscillations And Pressure Drop In Microfluidic Bubble Flows

Gas-liquid flows in the segmented/bubbly regimes are attractive alternatives to single-phase flow for chemical synthesis and analysis in microfluidic chemical systems due to their enhanced nonlinear mixing properties and reduced axial dispersion. Generation of stable, monodisperse bubble flows is critically dependent not only on the microchannel surface properties, gas/liquid flow velocities and fluid properties, but also on the details of the fluid delivery method and the geometric configuration of the microchannels.

Here we present high-speed gas-liquid flow visualization studies from two different fluid delivery methods into a microfluidic device with rectangular cross-section and T-junction based bubble generation. The electrical-hydraulic analogy is a useful tool in designing the fluidic network, so as to ensure stable, non-oscillating flow. An important component in formulating the fluidic network model for the system is the pressure drop of two-phase flow through the microchannels. In contrast to the linear, low-Reynolds number pressure drop of fluid flow through the individual gas and liquid lines, the two-phase pressure drop is non-linear and dependent on several factors. To explore this further, we present measurements of bubble size, breakup frequency, bubble velocity and gas void fraction in our experimental system. The above measurements are then used to explore the validity of available pressure drop models in the literature. The considerations highlighted in our work are critical in designing robust, scalable microfluidic two-phase flow networks for chemical processes.