Experimental Study Of A Piezoelectric Pump Based On Hydrophilic And Hydrophobic Surface Modification

Piezoelectric pump is a new type of fluid drive device, which is based on the inverse piezoelectric effect of piezoelectric ceramics. And It has a broad application prospect in biomedical, micro machine, portable detection equipment etc. But the existing piezoelectric pump is lack of stable working performance, mainly is extremely sensitive to the bubble, once air bubbles enter the pump chamber, the output flow and output pressure will drop sharply. If too many bubbles remain in the chamber, the piezoelectric pump may even lose their ability to work. These effects have greatly restricted its application.The domestic and foreign scholars have been exploring effective methods to improve the ability to discharge bubbles of the piezoelectric pump. Through some methods to improve the performance of the piezoelectric pump,which is structural innovation of piezoelectric pump and Improvement of material and structure of valve sheet,ect. This paper combines with this project “The mechanism, method and effect of wall wetting optimization for bubble control of piezoelectric pump” to carry out research,which is supported by the National Natural Science Foundation of China. The super hydrophilic / super hydrophobic surface modification was applied to the piezoelectric pump, and the experimental study was carried out to study the performance of bubble tolerant and the ability to discharge bubbles. Inorder to provide some methods to improve the output performance of the piezoelectric pump. The specific research contents are as follows:In this paper, the circular piezoelectric vibrator, which is made of PZT5 type piezoelectric ceramics, is used as the driver. The rectangular wave with high energy density is used as the driving signal, and the working mode of the piezoelectric vibrator is introduced. The theoretical model of piezoelectric vibrator is established, and the relationship between the displacement of the center point of the circular piezoelectric vibrator and the output pressure and the driving voltage of the piezoelectric vibrator is analyzed theoretically. The limit output performance of the piezoelectric vibrator is calculated,too. And on the basis of this, the effect of air bubbles on the output performance of the piezoelectric pump is analyzed. Then establishing the dynamic model of the piezoelectric pump with air bubbles, and the effect of the bubble on the output performance of the piezoelectric pump is analyzed further.The hight of the piezoelectric pump chamber, the structure and materials of the valve plate and the air bubbles are the main factors that affect the output performance of the piezoelectric pump.And the change of surface wettability will have some influence on the these factors. Through the theoretical analysis of these influencing factors and the corresponding experimental verification, the optimal chamber height of the experimental pump was determined as 0.15 mm. Selecting the wheel valve as the pump valve which is made of thickness 0.02 mm beryllium bronze.The effect of surface modification on the performance of the piezoelectric pump exhaust bubble is analyzed in detail and the corresponding results are given. The drag reduction effect of the super hydrophobic surface can increase the flow rate of the fluid in the pump cavity, but has strong adhesion to the bubble, which is not conducive to the discharge of the bubble. The super hydrophilic surface can reduce the adhesion of bubbles and increase the mobility of bubbles, which is conducive to the discharge of bubbles. Finally, according to the experimental requirements, we selected the super hydrophilic / super hydrophobic coating.Making experimental prototype and experimental test platform according to different wetting surface of the piezoelectric pump, the output flow rate and pressure when bubble inputted and ultimate bubble discharge experiments were conducted to study. The experimental results are as follows:1、 super hydrophilic treatment on piezoelectric pump cavity surface and the import and export valve, can improve the pump exhaust bubble ability, the effect of the former is more obvious; when they are both did super hydrophilic treatment, output performance of the pump is stable and air bubble ability is the strongest;2、 super hydrophobic treatment on piezoelectric pump cavity surface and the import and export valve, can not improve the ability of the piezoelectric pump exhaust bubble, and will have the opposite effect, the anti bubble ability is almost zero.3、 the output flow rate of the piezoelectric pump is about 0.32m/s, the change of surface wettability has little effect on the flow resistance of the flow channel, mainly through the retention of the bubble to affect the ability of exhausting bubble.