| Summary: | 碩士 === 國立交通大學 === 機械工程系所 === 94 === This thesis investigates experimentally the working principle of a valveless micropump with an open chamber actuated by a circular piezoelectric unimorph. Electrode of the piezoelectric buzzer is segmented into two semi-circular portions driven by singe-phase or dual-phase AC signals with a phase difference. The first symmetric mode, W00, and the first antisymmetric mode, W01, are excited to pump fluid inside the chamber. Resonant frequencies and corresponding vibration modes of the buzzer are calculated by using the finite element code ANSYS. Time-harmonic displacements of the unimorph induced by dual-phase signals are measured and simulated by superposition method. The experimental setup for measuring flow rate of the open-chamber micropump driven by a buzzer is after Hasegawa et al (2005). Experimental evidence indicates the resonant frequencies decrease due to fluid loading effect and by reducing the gap between leading tube and the buzzer. The maximum flow rate pumped by W00 mode is 133.13 ml/min and 9.63 ml/min by W01 mode. It occurs at the driving frequency slightly lower than the corresponding resonant frequency. The fluid loaded resonant frequencies for the buzzer whose backplane treated by hydrophobic process are lower than those without treatment. It results that a further formulation is needed to determine the resonant frequencies of fluid loaded structures exclusive of hypothesis of adding mass.
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