Jia Man,Luming Man,Chenchen Zhou,Jianyong Li,Shuaishuai Liang,Song Zhang,Jianfeng Li
Microfluidics devices have widely been employed to prepare monodispersed microbubbles/droplets, which have promising applications in biomedical engineering, biosensor detection, drug delivery, etc. However, the current reported microfluidic devices need to control at least two-phase fluids to make microbubbles/droplets. Additionally, it seems to be difficult to make monodispersed microbubbles from the ambient air using currently reported microfluidic structures. Here, we present a facile approach to making monodispersed microbubbles directly from the ambient air by driving single-phase fluid. The reported single-phase-fluid microfluidic (SPFM) device has a typical co-flow structure, while the adjacent space between the injection tube and the collection tube is open to the air. The flow condition inside the SPFM device was systematically studied. By adjusting the flow rate of the single-phase fluid, bubbles were generated, the sizes of which could be tuned precisely. This facile bubble generator may have significant potential as a detection sensor in detecting viruses in spread droplets or haze particles in ambient air.Keywords:microfluidic device;single-phase fluid;bubbles;air detection
Yang Xiaohan,Weldetsadik Netsanet Tesfaye,Hayat Zafar,Fu Taotao,Jiang Shaokun,Zhu Chunying,Ma Youguang
The aim of this work was to experimentally examine apparent rheological properties of fluids in microchannels based on pressure drop. Pressure drops of Newtonian and non-Newtonian fluids in microchannels were measured using pressure sensors. The effects of flow rate, Reynolds number, and viscosity of fluids on the pressure drop of single phase flow in microchannels were investigated, and the measurements of pressure drop were compared with prediction models. For Newtonian fluids, the friction factor in the laminar regime is f/ 2 = 26/ Re . The results show that the pressure drop of Newtonian fluid is in good agreement with the prediction formula proposed by Cornish. However, the pressure drop of non-Newtonian fluid deviates from the theoretical prediction. A power-law is proposed for the relationship between the apparent viscosity of non-Newtonian fluid and the characteristic shear rate in a microchannel based on the pressure drop measurement. This relationship between the apparent viscosity and the characteristic shear rate in a specific microchannel is completely different from the rheological curve measured by cone-and-plate rheometer, due to the heterogeneous distribution of shear rates at the radial direction for non-Newtonian fluids flowing in a microchannel.
Based on the split-and-recombine principle, a millimeter-scale butterfly-shaped microreactor was designed and fabricated through femtosecond laser micromachining. The velocity fields, streamlines and pressure fields of the single-phase flow in the microreactor were obtained by a computational fluid dynamics simulation, and the influence of flow rates on the homogeneous mixing efficiency was quantified by the mixing index. The flow behaviors in the microreactor were investigated using water and n-butanol, from which schematic diagrams of various flow patterns were given and a flow pattern map was established for regulating the flow behavior via controlling the flow rates of the two-phase flow. Furthermore, effects of the two-phase flow rates on the droplet flow behavior (droplet number, droplet size and standard deviation) in the microreactor were investigated. In addition, the interfacial mass transfer behaviors of liquid–liquid flow were evaluated using the standard low interfacial tension system of “n-butanol/succinic acid/water”, where the dependence between the flow pattern and mass transfer was discussed. The empirical relationship between the volumetric mass transfer coefficient and Reynold number was established with prediction error less than 20%.
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