Authors: Jian Yu, Wei Cheng, Jinchun Ni, Changwu Li, Xinggen Su, Hui Yan, Fubing Bao, and Likai Hou
Abstract
This work reports a simple bubble generator for the high-speed generation of microbubbles with constant cumulative production. To achieve this, a gas–liquid co-flowing microfluidic device with a tiny capillary orifice as small as 5 μm is fabricated to produce monodisperse microbubbles. The diameter of the microbubbles can be adjusted precisely by tuning the input gas pressure and flow rate of the continuous liquid phase. The co-flowing structure ensures the uniformity of the generated microbubbles, and the surfactant in the liquid phase prevents coalescence of the collected microbubbles. The diameter coefficient of variation (CV) of the generated microbubbles can reach a minimum of 1.3%. Additionally, the relationship between microbubble diameter and the gas channel orifice is studied using the low Capillary number (Ca) andWeber number (We) of the liquid phase. Moreover, by maintaining a consistent gas input pressure, the CV of the cumulative microbubble volume can reach 3.6% regardless of the flow rate of the liquid phase. This method not only facilitates the generation of microbubbles with morphologic stability under variable flow conditions, but also ensures that the cumulative microbubble production over a certain period of time remains constant, which is important for the volume-dominated application of chromatographic analysis and the component analysis of natural gas.
Fig 1. Microfluidic approach for generation of microbubbles with constant cumulative production. (A) Schematic illustration of microbubble generator and cumulative production in same period of time. (B) Microscopy image of microfluidic glass capillary device. (C) Generation of microbubbles. Scale bars are 100 μm.
Fig 2. (A) Number and diameter of microbubbles with different flow rates of liquid phase. (B) Cumulative microbubble production under different flow rates of liquid phase at gas input pressure of 150 kPa for 100 ms.
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Keywords: microbubble; microfluidic; cumulative production; generator; iFlow controller
Micromachines 2024, 15, 752