A MEMS based valveless micropump forbiomedical applications

[摘要] ENGLISH ABSTRACT: The valveless micropump holds great potential for the biomedical community in applicationssuch as drug delivery systems, blood glucose monitoring and many others. It is also a criticalcomponent in many a lab-on-a-chip device, which in turn promises to improve our treatmentand diagnosis capabilities for diseases such as diabetes, tuberculosis, and HIV/AIDS.The valveless micropump has attracted attention from researchers on the grounds of itssimple design, easy manufacturability and sensitive fluid handling characteristics, which areall important in biomedical applications.The pump consists of a pump chamber with a diffuser and nozzle on opposing sides of thepump chamber. The flow into the diffuser and nozzle is induced by an oscillating piezoelectricdisc located on top of the pump chamber. The nozzle and diffuser rectify the flow in onedirection, due to different pressure loss coefficients.The design process however is complex. In this study, we investigate the characteristics ofa diffuser / nozzle based micropump using detailed computational fluid dynamic (CFD) analyses.Significant parameters are derived using the Buckingham-Pi theorem. In part based onthis, the respective shapes of the diffuser and of the nozzle of the micropump are selected fornumerical investigation. Hence the influence of the selected parameters on the flow rate ofthe micropump is studied using three-dimensional transient CFD analyses. Velocity profilesfrom the CFD simulations are also compared to the Jeffery-Hamel solution for flow in a wedgeshaped channel. Significant similarities exist between the data and the predicted Jeffery-Hamelvelocity profiles near the exit of the diffuser.Three different diffuser geometries were simulated at three frequencies. The flow rate anddirection of flow are shown to be highly sensitive to inlet and outlet diffuser shapes, with theabsolute flow rate varying by as much as 200% for the geometrical perturbations studied. Entrancelosses at both the diffuser inlet and nozzle inlet appear to dominate the flow resistanceat extremely laminar flow conditions with the average Reynolds number of Reave ≈ 500.

[发布机构] Stellenbosch University