Principle,Structure,and Modelling Of A Piezoelectric-Actuated Microfluidic Pump Based On Circular Piezoelectric Unimorph Actuators

In the field of biological engineering,clinical medicine,microchips and micro total analysis system,there is an urgent need for devices and systems that can accurately deliver small quantities of the microfluids.Micropump,microvalve and microflow sensor are the key components for the control of the fluids in microfluid system.Micropump,as an essential part of the microfluidic system,has great potential in the application fields such as lab-on-a-chip,drug delivery,liquid cooling system,insulin therapy system and so on.The piezoelectric actuators have become the first choice of the actuators for developing high precision switching microfluidic valves or pumps due to their high resolution,high response speed,low power consumption,high output force density,and high accuracy.The active controlled microfluidic pumps based on the piezoelectric actuators have been studied in depth.Compared with the piezoelectric pumps with valves,the working efficiency of the valveless piezoelectric pumps can be improved.However,the working pressure and the cut-off performance of the pumps without check valves will be decreased abruptly.The advantage of the piezoelectric pumps with passive valves lie in the simple structure,while the disadvantages lie in the phase difference between the opening and closing of the valve and the drive,the response hysteresis,and the poor cut-off performance.Therefore,the piezoelectric pumps with passive valves are not suitable for the precise control of the microfluids.The piezoelectric-actuated microfluidic pump(PMP)based on circular piezoelectric unimorph actuators(CPUAs)is presented using the active controlled microfluid valves(ACMVs)with annular boundary as the inlet and/or outlet valves.The multi-chamber structure consists of two valve chambers of the ACMVs and one pump chamber,which are connected through their respective flow channels.The volume change of the pump chamber is simulated mathematically and analyzed according to the deflection characteristics of the CPUA actuated by the applied voltage.Meanwhile,the flowrate of the PMP is modeled by the theory of the gap flow between the parallel disks and the extended Bernoulli's equation.Finally,the flowrate and the backpressure of the PMP based on the CPUAs are tested by utilizing the established experimental setup.In order to make the PMP have better performance,its driving element-CPUA-was modeled and optimized.The major research works and the innovations in this dissertation are summarized as follows:1.The principle and structural configuration of an active controlled microfluidic valve(ACMV)with annular boundary is presented and developed.After the through hole and a coaxial circular ring chamber are manufactured on the valve,the annular boundary is naturally formed between the hole and the circular ring chamber.By coaxially covering the hole on the valve,the CPUA and the coaxial circular ring chamber formed a closed fluid chamber,if considering the through hole as the inlet connected to the inlet,the closed fluid chamber is connected to the outlet through the fluid passage.Through changing the applied voltage to the circular piezoelectric unimorph actuator,the gap height between the circular piezoelectric unimorph actuator and the annular boundary can be changed.The open,close,and the open level can be controlled to realize the flow control.2.The active controlled flowrate model of the active controlled microfluidic valve with annular boundary is established by using the classical laminated plate theory and the extended Bernoulli equation in fluid mechanics.The prototypes of the active controlled microfluidic valves with annular boundaries with three different combinations of the inner and outer radii are fabricated and tested on the established experimental setup.3.The structure of the core component of the ACMV and the PMP based on the CPUAs-the CPUA has been optimized to obtain the maximum flowrate,according to restriction conditions of the CPUA,combined with the optimization method of the multi-objective parameter.Through the optimization,the maximum gap height of the ACMV and the volume change of the PMP can be obtained,which can improve the flowrate of the valve and the PMP based on the CPUAs.4.The principle and structural configuration of the PMP based on the CPUAs are presented and developed.The PMP based on the CPUAs utilizes the ACMVs with annular boundary to constitute the inlet and outlet valves.The pump chamber is constituted by covering the CPUA with the open face of the cylindrical counterbore on the pump body.The valve chambers of the inlet and the outlet valves are connected to the pump chamber through the embedded fluid channels,respectively.The active controlled flowrate is achieved by changing the applied voltage to the CPUAs that constitute the ACMVs and the pump chamber.5.The flowrate and the backpressure of the PMP and the volume change of the pump chamber are simulated mathematically and analyzed.The volume change of the pump chamber is simulated mathematically and analyzed according to the deflection characteristics of the CPUA actuated by the driving voltage.Meanwhile,the flowrate of the PMP is modeled by the theories of the gap flow between the parallel disks and the extended Bernoulli equation.On this basis,the flowrate and the backpressure of the PMP and the volume change of the pump chamber are numerically simulated and analyzed.The prototype of the PMP is fabricated.The flowrate and the backpressure of the PMP based on the CPUAs are tested by the experimental system.In this paper,we research the basic characteristics of the PMP based on the CPUAs,the flowrate characteristics of the ACMV,and the model of the gap height between the actuator of the CPUA,which have laid a theoretical foundation for the structure optimization of the PMP based on the CPUAs and the application of the microfluid control system.