Development of a dual-phase miniature valve-less piezoelectric pump

摘要

This study investigated experimentally the working principle of a valve-less micro-pump with an open chamber actuated by a circular piezoelectric unimorph. In this pump, the electrode of the piezoelectric buzzer is segmented into two semi-circular portions driven by single-phase or dual-phase AC signals with a phase difference. The first symmetric mode, W00, and the first anti-symmetric mode, W01, are excited to pump fluid inside the chamber. For the experiments, the resonant frequencies and corresponding vibration modes of the buzzer were calculated by using the finite element code ANSYS, while the time-harmonic displacements of the unimorph induced by dual-phase signals were simulated and measured using the superposition method. The experimental setup for measuring the flow rate of this open-chamber micro-pump driven by a buzzer was the same as that previously described by Hasegawa et al (2005). The experimental results indicated that the resonant frequencies decreased due to the fluid loading effect and because the gap between the leading tube and the buzzer was reduced. The maximum flow rate pumped by the W00 mode was 133.13 ml/min, while the maximum flow rate pumped by the W01 mode was 9.63 ml/min. These maximum flow rates occur when the driving frequency is slightly lower than the corresponding resonant frequency.