Theoretical And Experimental Research On Piezoelectric Pump With The Piezoelectric Active Valve

The piezoelectric pump, using the deflection of piezoelectric diaphragm (PZT actuator) to transmit fluid, is a new-type fluidic device. It is an important part and researching focus in Microfluidic Systems. There are more than ten counties and regions all over the world in which there are the research institutions of the piezoelectric pump. With many merits such as simple structure, small body, no interfere of electromagnetism and good output ability under low applied voltage etc, the piezoelectric pump has very extensive application prospects in the fields of chemical analysis, medical treatment, pharmacy and bioengineering etc. Although the piezoelectric pump has been researched and developed for more than twenty years, the research is mainly focusing on the piezoelectric pump with passive valves. The working passive valve has, however, the response hysteresis with the actuator and low cut-off ability. As for the active valve, adopting the actuator to control the working of valve, it has the great controllable ability. And the active valve with flexible application ways can be used in both micropump and Microfluidic Systems substantive. The active valve consists of the passive valve and the actuator, so the methods used to actuate the micropump are all can apply to the active valve. As a result, there is the great research value and space of the active valve, In this paper, the selective principles of the active valve with piezoelectric actuator are put forward by the integrative analysis of all kinds of microvalves. The working principles of the piezoelectric pump with the piezoelectric actuated active valve are expatiated comprehensively. The vibration modes of the PZT bimorph, which is the actuated part of the piezoelectric pump, are analyzed in detail. The prototypes of the piezoelectric pump with the piezoelectric actuated active valve are fabricated and the experiments about performance of the pumps have been done.1. Analysis and experiments on the piezoelectric bimorphThe piezoelectric bimorph is the key part of the pump, so to find out itsstructure and working characters has the very important significance on improving the output performance of the pumps, hi this chapter, the piezoelectric effect, piezoelectric materials and the structure of piezoelectric bimorph are presented. The vibration equation of the PZT bimorph is educed by using the sheet vibration theory and the related piezoelectric knowledge, and the central displacement formula is worked out.The experiments on the distortion of the piezoelectric bimorph show that the distortion of piezoelectric bimorph and the actuated voltage present the linear relation, so adjusting the actuated voltage can obtain the required distortion. Moreover, the distortion of piezoelectric bimorph can also be influenced by the actuated frequency and the shape of the actuated voltage. With different actuated voltage signals, the distortions of piezoelectric bimorph are different as well. Comparing the three shape of the actuated voltage, the sine wave gains the biggest distortion and the rectangular wave gains the smallest distortion. Given the different actuated frequencies, the distortions of piezoelectric bimorph have remarkable distinction. So the actuated frequency and the shape of the actuated voltage are taken as the influence factors to study the dynamic distortion of piezoelectric bimorph. Load also influences the distortion greatly. Without load, there is favorable linear relation between the distortions of piezoelectric bimorph and the actuated frequency; with load, there is the optimal corresponding point between the distortions of PZT actuator and the actuated frequency.2. The research on the characteristics of the piezoelectricactuated active valveThe piezoelectric actuation is selected for the pump with the comprehensive analysis of the structures and characteristics of all kinds of micro valves. The PZT element, with the series merits such as high resolving, sharp response, free-friction and fray, low consuming of power, against magneti...