Structural Design And Experimental Study Of A Wheatstone Bridge Valveless Piezoelectric Pump

Due to low power consumption,high accuracy and no electromagnetic interference,piezoelectric pumps has become a substitute for traditional pumps in drug delivery,cell transportation,chip cooling and other industries,which has great application value.Piezoelectric pump is s system integrating pump chamber,valve and actuator,which not only overcomes the leakage,abrasion and fatigue damage caused by moving parts,but also reduces the energy loss at connection between different components in traditional pumps.Generally,according to the features of the valve configuration,the piezoelectric pumps can be classified into valve piezoelectric pumps and valveless piezoelectric pumps.Under high working frequency,the valve piezoelectric pumps is prone to fatigue and abrasion which is susceptible to valve of the hysteresis.Compared with valve piezoelectric pumps,valveless piezoelectric pumps has no moving parts,greatly improving its working frequency.At the same time,valveless piezoelectric pumps allowing fluid with micro particles,are suitable for biomedicine,chemical analysis,etc.To realize the miniaturization and functional diversification of pump,the structural design of external functional valve body or asymmetric pump chamber is adopted.External functional valve body needs to take up a large space resources,which is not conducive to miniaturization.Although asymmetric pump chamber has the advantages of good connection versatility and strong flow control,the existing flow shock and fluctuation in pump chamber also bring obstacles to application.Meanwhile,with the improvement of microfluidic technology,the system with multi-functional parts requires more working frequency segments.Therefore,wide working frequency for components will lead to the phenomenon of mutual interference between different components at the same frequency.And the working frequency of existing piezoelectric pumps is relatively wide,which is not conducive to the choice of working frequency for other parts.According to the features of tight structure for Wheatstone bridge circuit,this paper aims to construct a Wheatstone Bridge type valveless piezoelectric pump(WBTVL PZT pump)with compact structure and narrow working frequency range.And it will focus on structure design of WBTVL PZT pump,theoretical analysis,finite element analysis,experimental verification and structural optimization.The specific research content is as follows:(1)The structural design and theoretical analysis of WBTVL PZT pump were carried out.After the structural design of flow channel in Wheatstone bridge type(WBT),the selection of piezoelectric vibrator,runner size design and the overall structural design of the pump were realized..Based on fluid continuity and energy conservation,the flow resistance analysis and expression derivation of flow rate for the pump are carried out.In addition,the working principle of piezoelectric pumps is described.(2)The finite element analysis of WBT flow channel and pump was carried out.Firstly,flow field of flow channel is simulated under different pressure differences.Then the flow resistance characteristics of the flow channel are obtained,which verifies that the flow channel has the characteristics of a valve.Then the transient calculation and analysis of the flow field inside the whole pump are carried out.And the speed streamline contours of the suction stage and the discharge stage are obtained,which proves that the WBTVL PZT pump has pump effect.(3)The experimental study of WBTVL PZT pump was carried out.Pump prototypes were fabricated by 3D printing technology and experimental platform was constructed.The accuracy of the simulation results was verified by the flow resistance test of the convection tube.The relationship between amplitude of piezoelectric vibrator and parameters of input signal was explored.Then,the relationship between the output performances of prototype is discussed under different voltages and frequencies,which concludes that the effective working frequency range of the voltage pump is narrow.Finally,to verify the fluidity of pump,a high-speed camera was used to observe and record the fluid movement in a pumping cycle.(4)For the optimization design of the pump,the influences of volume change and turbulence effects on the output performance were explored.As optimization object,height of pump chamber,size of flow channel,length of conical tube,taper size of conical tube,as well as the contact ratio between the center of WBT flow channel and the center of pump chamber were considered,using the control variable method.The related experiments were carried out and the optimal pump parameters are obtained.