Geometrical tuning of microdiffuser/nozzle for valveless micropumps

Valveless micropumps require the integration of microdiffusers/nozzles for flow rectification in microfluidic systems. The flow directing capability of a micropump is determined by the efficiency of the diffuser. With the reduction in size of the micropump, conventional microdiffuser geometrical parameters are not suitable for obtaining high flow efficiencies due to several fluidic effects such as channel friction, wall shear stress, vena contracta, etc, and therefore it is important to modify the diffuser geometry according to the requirements of the pressure coefficients in order to obtain improved flow rates. This paper presents a simple and microfabrication friendly geometrical tuning method which offers the user a broad range of dependent tunable geometric parameters to improve the performance of the microdiffuser for valveless micropumps. Herein, for a given flow condition, the flow behaviour and the variation of pressure coefficients of the microdiffuser/nozzle with geometric tuning have been studied for different diffuser angles using finite element modelling (FEM). The results show that the proposed method is highly suitable for tuning the geometry of microdiffusers for a wide range of operating conditions of valveless micropumps. The performances of the best diffuser geometries for different diffuser angles have been experimentally verified, and the test results are used for the validation of the results of the FEM. The comparison between the FEM and experimental results shows a close agreement.