| Summary: | 碩士 === 國立中興大學 === 機械工程學系 === 91 === This study reports flow visualization results on mixing of two fluids in microfluidics. The fabrication of microfluidic chips adopts the micromachining techniques of MEMS (Micro-Electro-Mechanical System) to construct simple geometric microchannels that provide as the device for observation of mixing process. These channels are mainly designed as T-type, and a structure of convergent and/or divergent is inserted between the intersection of these channels to observe the change of flow field and mixing characteristics. Images of flow field are captured with the CCD camera. Sodium hydroxide and phenolphthalein solutions were dissolved in ethyl alcohol respectively. These two colorless fluids would become red during the mixing process, and the consistency of color intensity is taken as a mixing index. Quantification of mixing efficiency of the fluids is instituted using the mixing indices. It is found that the mixing efficiency determined from the aforementioned method shows an essentially consistent value even employing different color intensities of RGB. In addition, the mixing-interface becomes unstable when the flow rate exceeds a certain value that is associated with geometry of the channel. In general, the instability is enhanced, showing larger oscillation amplitude, for higher flow rate. Details on the interface instability demand further analysis.
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