Flow Rate Of Micro-diffuser And Mixing Behavior Of Micro-channel In Biochips

Micro-diffuser is one of the most important elements of valve-less piezoelectric micropumps in biochips. For the purpose of optimal design of micro-diffuser, numerical study of flow characteristic and flow rate of a flat-walled diffuser was carried out in this study. Dimension analysis shows that directional flow rate of micro-diffuser depends on four dimensionless parameters: Reynolds numbers, the ratio of length to width, ratio of depth to width and diffusion angle. This study performed numerical calculations of three-dimensional flows in a micro-diffuser using the CFD software FLUENT, and gave quantitative relationships of diffuser flow rate and four parameters. The optimal parameter ranges for diffuser are also proposed in this paper based on numerical results. This paper also adopts numerical method to study periodical flow characteristics and liquid mixing process of biological sample and chemical reagent in a serpentine micro-channel. Four flow cases are investigated:(1) steady flows in a straight micro-channel with rectangular section; (2) periodical flows with non-zero flow rate in a straight micro-channel with rectangular section; (3) steady flows in a serpentine micro-channel with rectangular section; (4) periodical flows with non-zero flow rate in a serpentine micro-channel with rectangular section. Numerical results indicate that liquid mixing efficiency in micro-channel increases in sequence from case (1) to case (4). Investigations of flow characteristics reveal that unsteady multi-crest velocity profile of the periodical flows and secondary flows of serpentine micro-channel greatly enhance liquid mixing.