**6. Conclusions**

V

V This paper discussed a piezoelectric resonance pump with a flexible support, which took a square piezoelectric vibrator as the driving unit. After analyzing the working principle and establishing a dynamic model of the vibration system, prototypes with different structural parameters were made and tested. Finally, the experimental results were provided to show several performance indexes to optimize the pump system.

A vibration test of the piezoelectric resonance pump was carried out. The results show that the pump resonated at 236 Hz when pumping air. When the peak-to-peak voltage of the driving power was 220 V, the amplitude of the diaphragm reached a maximum value of 0.43933 mm, and the volume change of the pump improved. This suggests that the flexible supported square piezoelectric vibrator can effectively reduce the constraints of fixed installation with its own vibration.

For the results of the performance test of the piezoelectric resonance pump show that when the pump chamber height was 0.25 mm, the output flow rate reached the maximum value of 213.5 mL/min. When the chamber height was 0.15 mm, the output pressure reached the maximum value of 85.2 kPa. This indicates that the chamber height directly affected the liquid compression ratio in the pump chamber. Increasing the chamber height means that the liquid compression ratio decreased, thereby reducing the output pressure.

Finally, the check valve comparison test showed that it is vital to select a wheeled check valve with suitable stiffness according to the frequency for a piezoelectric resonance pump working at a specific resonance frequency. An appropriate check valve can improve the pump's output performance.

**Author Contributions:** J.W. designed the concept and organized the study. X.Z. conducted the experiment and analyzed the experiment results. X.C. completed the assembly and production of the prototype and assisted in the prototype test. H.Y. assisted in the manuscript preparation. All of the authors contributed in writing the manuscript.

**Funding:** This research was funded by Doctoral Fund of Yanshan University, gran<sup>t</sup> number BL18052, and China Postdoctoral Science Foundation, gran<sup>t</sup> number 2018M631765.

**Acknowledgments:** This study was supported by the Doctoral Fund of Yanshan University (Grant No.BL18052).

**Conflicts of Interest:** The authors declare no conflict of interest.
