Pseudo-resonance phenomenon of valveless piezoelectric pump

Abstract

Volumetric piezoelectric pumps are widely used in the field of microfluidic drive due to their simple structure, flexible design, and absence of magnetic interference. As driven by the volume change of the pump chamber, the majority of this kind of pumps work under the first order resonance frequency, where the volume change is the largest. However, the experimental parts or data of many studies reflect a phenomenon that a flow rate peak exists in the non-resonance frequency range. This phenomenon has not been studied or explained in depth, and goes against conventional vibration theories. In this study, we define this phenomenon as the pseudo-resonance phenomenon, and the corresponding flow rate peak is named as the pseudo-resonance flow rate peak. First, a non-single-channel composite tapered tube valveless piezoelectric pump (NCTVP) was designed, which reproduced the pseudo-resonance phenomenon reported in the literature. Through displacement measurement experiments, it was demonstrated that the vibration mode of the piezoelectric vibrator was B00 mode when the pseudo-resonance phenomenon occurred. Then, frequency sweeping experiments and flow field observation experiments were conducted, it can be obtained that the pseudo-resonance phenomenon is caused by the reaction force of the water to the piezoelectric vibrator, and the reaction force is generated by the impact of two streams. Finally, based on the experiment results, a theoretical model was established; it was deduced that the first order resonance flow rate peak was caused by the flow resistance difference between the forward and reverse flows of the tapered tubes in NCTVP, and that the pseudo-resonance flow rate peak was caused by the water hammer effect. By applying the pseudo-resonance phenomenon, another flow rate peak was obtained in the non-resonance frequency range without changing the mechanical structure, which can enable piezoelectric micro nano pump to obtain extra flow rate or pressure without changing the constraint boundary conditions.