| The prevalence of fluid accumulation diseases such as hydrocephalus and lymphedema is increasing year by year,which seriously affects human health.Tissue effusion needs to be drained or shunted in a timely,accurate and quantitative manner to prevent complications such as tissue infection and toxic shock.At present,the shunt of tissue effusion still has certain defects,such as the shunt tube cannot adjust the pressure and cannot resist gravity.The micropump has the advantages of portability,light weight and accurate dose,and has broad application prospects in the field of disease treatment of timely and quantitative shunting of tissue fluid.The existing medical micropumps have problems such as large structure,high driving voltage and unadjustable flow rate,which hinder their development in the field of treatment of diseases such as hydrocephalus and lymphedema.This paper focuses on the study of a flow-adjustable piezoelectric valveless micropump for tissue effusion shunt treatment.Using the innovative structural design of the double-layer pump chamber,a wide range of flow output can be achieved under the condition of low voltage drive and miniaturization.The specific research contents are as follows:(1)The theoretical model of driving,rectification and flow of the double-layer pump chamber piezoelectric valveless micropump is established.A theoretical deformation model of the piezoelectric vibrator was established,the analytical relationship of the vibration amplitude during the driving process of the piezoelectric vibrator is deduced,and the key parameters affecting the volume change of the pump chamber are analyzed.The geometric model of the nozzle/diffuser microvalve is established,the pressure loss coefficient and rectification efficiency of the microvalve in the double-layer pump chamber structure are analyzed,and the influence of the characteristic parameters of the microvalve on the rectification efficiency is explored.Based on the analysis of the working theory of the piezoelectric vibrator and the nozzle/diffuser microvalve,the calculation formulas of the net flow and the working efficiency of the micropump are deduced.Theoretical analysis shows that the square of the pump chamber diameter and the voltage are proportional to the output flow,and the throat width and divergence angle of the microvalve directly affect the working efficiency of the micropump.(2)Design the size and structure of the double-layer pump chamber piezoelectric valveless micropump,and establish the multiphase coupling simulation model of the piezoelectric vibrator and the micropump.For the piezoelectric vibrator,the variation of the amplitude with the voltage and the distance from the center is obtained by the piezoelectric coupling simulation,and the mode shape of the piezoelectric vibrator is studied by modal analysis combined with parameter scanning.Aiming at the overall structure of the micropump,an electric-solid-fluid three-phase coupling simulation model is established to analyze the influence of the microvalve,the depth of the pump chamber,the driving voltage and the frequency on the flow rate of the micropump.The optimization simulation results show that the optimal design size of the double-layer pump chamber micropump structure is as follows:the throat width of the microvalve is 300 μm,the divergence angle is 30°,and the depth of the upper pump chamber is 100 μm.The double-layer pump chamber piezoelectric valveless micropump is suitable for low-frequency driving,and the net flow increases with the increase of driving voltage.(3)Multi-process combination to make a double-layer pump chamber piezoelectric valveless micropump,and experimentally test the output flow of the micropump.Combining photolithography technology with laser cutting technology,oxygen plasma treatment and chemical surface coating method,the bonding and fabrication of double-layer pump chamber piezoelectric micropump devices are realized.The variation of output flow with microvalve divergence angle,throat width,upper pump chamber depth,frequency and voltage is measured.The experimental results show that the optimal design parameters of the microvalve are the same as the simulation results,the throat width is 300 μm,the divergence angle is 30°,and the depth of the upper pump chamber is 100 μm.The flow rate of the micropump increases with the increase of the voltage,and the output flow range is 2.16～51.74μL/min under the voltage of 12～28 V,which verifies the effectiveness of the double-layer pump chamber structure to improve the flow rate and the feasibility of applying to tissue effusion shunting. |
