Modeling Microfluidic Microbubble Generators

In this paper, two microfluidic bubble generators are proposed and modeled using COMSOL^®. The first device consists of two microchannels perpendicular to each other. This arrangement of channels has been successfully used for generating bubbles with diameters in the millimeter range previously. The feasibility of miniaturizing this structure has been investigated in this paper. The bubble diameter generated using this method is found to vary inversly with the liquid flow rate (i.e. flow velocity). This is disadvantageous in terms of pressure drop while trying to generate microbubbles in microchannels. Therefore a second device, an extension of the first, has been proposed for eliminating this drawback by introducing a solid structure in the liquid channel right in front of the gas channel. The suitability of this device as a microbubble generator is checked through COMSOL^® simulation model. At low flow rates, the bubble diameter is not significantly affected by the presence of the solid structure in the microchannel. In both devices the bubble attached itself to the walls at low Reynolds number but this did not happen at high Reynolds number. Further investigations are done in this study for understanding the effect of different shaped structures on the diameter of the microbubble.