Theoretic And Experimental Research On Pulsed Centrifugal Diaphragm Piezoelectric Pump

The piezoelectric pumps are novel fluid actuators. Which are miniature structure, fast response, high accuracy, low power consumption and low noise. These features make piezoelectric pumps be applied to micro electro-mechanical devices, medical instruments and biopharmaceuticals, chemical analysis, aerospace and other areas with great performance. For reciprocating displacement piezoelectric pumps, the mechanical membranes or flaps often used in check valve pumps show a serious lag in frequency response, making it difficult to work with piezoelectric actuator synchronously. Compared with passive check valves, piezoelectric active valves increase the operating frequency of the pump, but they have problems of small opening displacement or small output force, which induces drop in flow rate. In high frequency pumping, it is not easy to coordinate operation of pump vibrator and valve vibrator. And the valve control system is complex and difficult in integrated design. Using MEMS technology to produce new check valves with excellent high frequency characteristics is an alternative way, but the manufacture and control of these micro valves have several drawbacks, e.g., complex design, difficult manufacturing, high cost and difficult promoting.In order to effectively coordinate the high frequency characteristics of piezoelectric materials and low frequency characteristics of check valves in conventional piezoelectric pumps, a pulsed centrifugal diaphragm piezoelectric pump is introduced in this thesis. Piezoelectric elements work at a relatively high frequency while check valves operate at a low frequency, and they work together coordinately with no conflicts. It utilizes centrifugal force in the swing motion of a vibrating tube to drive liquid within the tube to flow, and the diaphragm in the pump chamber is deformed, thereby changing the volume of the pump chamber and completing liquid delivery by check valves. Firstly, working principle of the pump is explained. Secondly, dynamic modal of the driving part of the pump is established and dynamic character including resonant frequency, vibrating mode shape, centrifugal force and vibrating amplitude limit are studied. Finally, a prototype pump was fabricated. Pump characters including admittance, pulsation, flow rate and backpressure are measured to verify theoretic results. Build a fast start-up and fast-stop control circuit in order to increase the output flow rate of the pump. This control circuit capable of frequency tracking is designed. In addition, based on principle of pulsed centrifugal diaphragm piezoelectric pump, This thesis proposes a novel piezoelectrically driven pipette,which utilizes centrifugal force in swing motion of a vibrating tube as the driving force, to input and output liquid at first bending resonant frequency. Pulse volume changing with different driving voltage amplitude, driving frequency, tip size and target reagents are studied in experiments.Experimental results show that the Prototype pump can hold and discharge very precise volume of liquid in every pulse, and can pump deionized water at a flow rate of6.12ml/min under a backpressure of0.3kPa with driving voltages of560Vpp, vibrating frequency of183.74Hz, absorbing period of0.4s and dispensing period of0.1s. The experimental results validate the feasibility of pulsed centrifugal diaphragm piezoelectric pump. Using the control circuit, flow rate increase to12.49ml/min under a pulsation frequency at4Hz, property improved.The output pulse volume of a prototype pipette driven by voltage of560Vpp at175.9Hz is43.2μL with a variation of±3.5%. Minimum water spots of3(μL can be deposited in this manner. This pipette represents an alternative to standard liquid transfer techniques in chemical or biological experiments.