Using No-Moving-Part(NMP) valve in microfluidic systems has been one of the most effective methods for traort and delivery of unidirectional flow. Instead of external mechanism, fluid flow behavior is responsible for the variation in pressure drop between forward and reverse flow in NMP valves. Such microvalves have been widely used as check valves in the construction of diaphragm micropumps. In this study two important types of NMP valves including nozzle-diffuser microvalve and Tesla microvalve have been investigated and a new designed shape is proposed for the Tesla valve based on numerical analysis of fluid flow inside the valve. The main criterion used for evaluation of valve performance was Diodicity which can be defined as the ratio of pressure loss in the reverse-flow direction to loss in forward direction at identical volume flow rate. Comparison with previous types proved the superiority and novelty of proposed valves. Besides, a three dimensional modeling of a diaphragm micropump together with the proposed valves was carried out. Piezoelectric device was chosen as the actuator of the micropump. The simulation showed that the new system is more efficient than conventional nozzle-diffuser micropump considering both maximum pressure head and flow rate. In the next step, the efficiency and performance of piezoelectrically actuated micropump was investigated based on driving voltage wave shapes. Square shape excitation with the sharpest instantaneous slope had the most notable flow rate compared to the other types in the examined range of frequencies. However the power requirement of sawtooth wave shape was much lower than square excitation. The second approach used for design and analysis of the diaphragm micropump with piezoelectric actuation was equivalent circuit modeling. This model predicts the frequency response of the complete system given the characteristic of the pump components and pump loads. In the proposed model, the new designed valve was modeled by introduction of a nonlinear resistance to the circuit. As a practical application, the possibility of using the proposed micropump for fuel delivery in a Direct Methanol Fuel Cell(DMFC) was also investigated both qualitatively and quantitatively. Finally the numerical models were experimentally validated by real prototype fabrication of the new micropump. There were a good agreement between three dimensional simulation and electrical modeling of the micropump. The general trend was also the same for both numerics and experiment. However some deviations were observed. These deviations can be explained considering fabrication limitations and some simplification in computer modeling. Key words: Tesla microvalves, Diodicity, Micropump, Multi-Physics, Equivalent circuit modeling
