基于MEMS的压电微泵建模与优化

以压电驱动的无阀微泵为研究对象,根据扩张管/收缩管的压力损失系数和连续方程,建立了无阀微泵的理论模型。利用有限元分析软件,建立了无阀微泵有限元模型,进行了耦合场仿真分析。模拟并分析了不同边界条件下驱动电压、电压频率、泵膜厚度、压电薄膜厚度和压电材料对无阀微泵输出特性的影响。仿真结果显示,无阀微泵具有很好的整流特性,并且驱动电压越大,输出特性越好。在局部固定边界条件下,当压电薄膜上施加电场强度为500 V/mm的驱动电压时,存在最优的压电薄膜厚度,使得微泵的输出流量最大。研究结果为无阀微泵的优化设计提供了依据。     

Design and analysis of a double superimposed chamber valveless MEMS micropump

The newly designed micropump model proposed consists of a valveless double chamber pump completely simulated and optimized for drug delivery conditions. First, the inertia force and viscous loss in relation to actuation, pressure, and frequency is considered, and then a model of the nozzle/diffuser elements is introduced. The value of the flowrate obtained from the first model is then used to determine the loss coefficients starting from geometrical properties and flow velocity. From the developed model IT analysis is performed to predict the micropump performance based on the actuation parameters and no energy loss. A single-chamber pump with geometrical dimensions equal to each of the chambers of the double-chamber pump was also developed, and the results from both models are then compared for equally applied actuation pressure and frequency. Results show that the proposed design gives a maximum flow working frequency that is about 30 per cent lower than the single chamber design, with a maximum flowrate that is 140 per cent greater than that of the single chamber. Finally, the influences of geometrical properties on flowrate, maximum flow frequency, loss coefficients, and membrane strain are examined. The results show that the nozzle/ diffuser initial width and chamber side length are the most critical dimensions of the design.     

Simulation of the fluidic features for diffuser/nozzle involved in a PZT-based valveless micropump

PZT-based valveless micropump is a microactuator that can be used for controlling and delivering tiny amounts of fluids, and diffuser/nozzle plays an important role when this type of micropump drives the fluid flowing along a specific direction. In this paper, a numerical model of micropump has been proposed, and the fluidic properties of diffuser/nozzle have been simulated with ANSYS. With the method of finite-element analysis, the increased pressure drop between inlet and outlet of diffuser/nozzle induces the increment of flow rate in both diffuser and nozzle simultaneously, but the increasing rate of diffuser is faster than that of nozzle. The L/R, ratio of L（length of cone pipe） and R （radius of minimal cross section of cone pipe） plays an important role in fluidic performance of diffuser and nozzle as well, and the mean flow rate will decrease with increment of L/R. The mean flow rate reaches its peak value when L/R with the value of 10 regardless the divergence angle of diffuser or nozzle. The simulation results in-dicate that the fluidic properties of diffuser/nozzle can be defined by its geometric structure, and accordingly determine the efficiency of micropump.     

静电微泵的3D流固耦合动态特性分析

采用任意拉格朗日—欧拉(ALE)描述建立了无阀微泵的静电-结构-流体全耦合三维模型,数值仿真表明:泵内流体的动态特性与泵膜的运动存在着密切的关系;扩散/收缩口单元两端的压力差必须达到一定值后才有"整流"泵送效用;泵腔内流体压力的分布几乎一致;流体流动的最大雷诺数远小于宏观条件下认定的临界雷诺数;流体黏滞损失的非线性不容忽视。     

Simulation and optimization of a piezoelectric micropump for medical applications

We designed a valveless micropump excited by a piezoelectric actuator for medical applications. The complete electric–fluid–solid coupling model is built upon using ANSYS software (Canonsburg, PA) to investigate the behaviors of the micropump. The effects of the geometrical dimensions on the micropump characteristics and its efficiency are analyzed. The simulation results show that there is an optimal thickness of the piezoelectric layer to obtain a large pump flow, and that this optimal thickness is affected by the material and the thickness of the pump membrane. To enhance the performance of the micropump, some important diffuser parameters, such as the diffuser length, the diffuser angle, and the neck width, should be optimized. However, the variations of the diffuser’s geometrical dimensions do not affect the optimal thickness of the piezoelectric layer.     

A bidirectional valveless piezoelectric micropump with three chambers applying synthetic jet

A new type of valveless piezoelectric micropump is presented. Synthetic jet and Coanda effect are utilized to achieve larger and bidirectional flow rate. The numerical simulation applying the velocity and pressure boundary conditions as well as the SST turbulence model were utilized to research the performance and internal flow state of the micropump. The simulation method was tested by the previous experimental data and the results matched well. The results suggest that the flow rate of the micropump is related to the Reynolds number and frequency. The entrainment flow rate of synthetic jet accounts for over 80% of the total outflow rate. The outflow rate is much larger than the volume change of the micropump chambers. There is an optimal frequency to obtain the maximum flow rate regarding the volume change of the chambers as a constant. The fluctuation of the flow rate decreases with the increase of frequency. When the frequency is higher than 25 Hz, the outflow can be continuous. Working at the Reynolds number of 1000 and optimal frequency of 50 Hz, the flow rate is 6.8 ml/min.     

Piezoelectric diffuser/nozzle micropump with double pump chambers

To eliminate check valve fatigue and valve clogging, diffuser/nozzle elements are used for flow rectification in a valveless diffuser/nozzle micropump instead of valves. However, the application of this type of micropump is restricted because of its pulsating or periodic flow and low pump flux. In this paper, a diffuser/nozzle Si/Glass micropump with two pump chambers by IC and MEMS technology is designed. The fabrication process requires only one mask and one etch step, so that the fabrication has the advantages of low cost, short processing period, and facilitation of miniaturization. The pump is equipped with a glass cover board so as to conveniently observe the flow status. Pump-chambers and diffuser elements are fabricated by the anisotropic KOH-etch technique on the silicone substrate, and the convex corner is designed to compensate for an anisotropic etch. The driving force of the micropump is produced by the PZT piezoelectric actuator. The pump performance with both actuators actuated in anti- or same-phase mode is also researched. The result indicates that the micropump achieves great performance with the actuators working at anti-phase. This may be because the liquid flows steadily, pulse phenomenon is very weak, and the optimal working frequency, pump back pressure, and flow rate are both double that of the pump driven in same-phase.     

Piezoelectric diffuser/nozzle micropump with double pump chambers

To eliminate check valve fatigue and valve clogging, diffuser/nozzle elements are used for flow rectification in a valveless diffuser/nozzle micropump instead of valves. However, the application of this type of micropump is restricted because of its pulsating or periodic flow and low pump flux. In this paper, a diffuser/nozzle Si/Glass micropump with two pump chambers by IC and MEMS technology is designed. The fabrication process requires only one mask and one etch step, so that the fabrication has the advantages of low cost, short processing period, and facilitation of miniaturization. The pump is equipped with a glass cover board so as to conveniently observe the flow status. Pump-chambers and diffuser elements are fabricated by the anisotropic KOH-etch technique on the silicone substrate, and the convex corner is designed to compensate for an anisotropic etch. The driving force of the micropump is produced by the PZT piezoelectric actuator. The pump performance with both actuators actuated in anti-or same-phase mode is also researched. The result indicates that the micropump achieves great performance with the actuators working at anti-phase. This may be because the liquid flows steadily, pulse phenomenon is very weak, and the optimal working frequency, pump back pressure, and flow rate are both double that of the pump driven in same-phase.     

无阀微泵动态特性的固液耦合分析

根据无阀微泵的工作原理,对泵膜－流体耦合振动过程进行理论分析,推导出此状态下的非线性耦合振动方程,并采用伽辽金加权最小余量法得出方程的近似解。在此基础上讨论阻尼系数、驱动力及薄膜固有频率与薄膜振幅、相位差及无阀泵流量的关系。理论分析表明在阻尼系数较小时,在一阶固有频率附近还存在振幅增大的现象,随着阻尼系数的增大,流体对泵膜的阻力逐渐增大,振幅随着频率的增大迅速衰减,相位差也越来越快地靠近90°;驱动力一定的情况下,薄膜的固有频率越低,薄膜在低频段振动可以达到的振幅越大;对于流量而言,在低频段,流量很快就达到极大值,而且阻尼系数越大、泵膜固有频率越低、驱动力越大,流量越快到达极大值。     

无阀压电微流体泵工作特性与结构参数

根据平面无阀压电微流体泵的结构特点,采用厚度平均的浅水模型和有限元法,得到微流体泵液体－振动片耦合方程。耦合方程的模态分析给出硅片一阶模态自然频率和振型,以及硅片振幅－频率关系。在模态分析之后,加入压电力考察振动片响应、微泵流动特征和微泵流量。同时研究微泵结构参数(微泵压电片半径、扩散管长度、最小宽度、扩散张角)对微流体泵液—固耦合系统的自然频率、振动片振幅和微泵流量的影响,得出对微流体泵优化设计有重要意义的结果。     

负压驱动蠕动微型泵的研究进展

基于负压驱动原理研制了一种结构简单的蠕动微型泵。微型泵由3层聚二甲基硅氧烷(PDMS)材料,构成气路层、驱动薄膜层和流路层,其全部结构均采用激光器加工制作而成,并通过表面等离子体氧化处理技术实现了各PDMS层之间的键合封装。该微型泵具有流速高、回流低、气泡耐受能力强,以及不伤害传送介质的特点。尤为重要的是,连接负压源的气路层通过PDMS薄膜能有效去除流路中的气泡,这是处理复杂流体样品时所期望的。通过对比前期微型泵的气路通道的流阻、常闭微阀的个数、负压压力和驱动频率等各项参数,获得了其性能参数。在50kPa负压和30Hz驱动频率的条件下,获得的最佳流速为600μL/min,这一流速参数可与正压气动型蠕动泵的流动性能相媲美。     

Electro-magnetically actuated valveless micropump with two flexible diaphragms

We present a parallel dynamic passive valveless micropump, which consists of three layers-valve, diaphragm and electromagnetic coil. The valve is wetly etched in a silicon wafer, the diaphragm is a polydimethyl siloxane (PDMS) film spun on a silicon wafer with embedded permanent magnet posts, and the coil is electroplated on a silicon substrate. Under the actuation of the magnetic field of the coil, the flexible diaphragm can be displaced upwards and downwards. After analyzing magnetic and mechanical characteristic of the flexible membrane and direction-dependence of the nozzle, this paper designed a micropump. And the relative length (L/d) of the micropump's nozzle is 4. A 7×7 array of permanent magnetic posts is embedded in the PDMS film. Two diaphragms work in an anti-step mode, which can relieve the liquid shock and increase the discharge of the micropump. ANSYS and Matlab are adopted to analyze the actuation effect of the coil and the flow characteristic of the micropump. Results show that when actuated under a 0.3 A, 100 Hz current, the displacement of the diaphragm is more than 30 μm, and the discharge of the micropump is about 6 μL/s.     

Multi-Field Analysis and Experimental Verification on Piezoelectric Valve-Less Pumps Actuated by Centrifugal Force

A piezoelectric centrifugal pump was developed previously to overcome the low frequency responses of piezoelectric pumps with check valves and liquid reflux of conventional valveless piezoelectric pumps. However, the electro-mechanical-fluidic analysis on this pump has not been done. Therefore, multi-field analysis and experimental verification on piezoelectrically actuated centrifugal valveless pumps are conducted for liquid transport applications. The valveless pump consists of two piezoelectric sheets and a metal tube with piezoelectric elements pushing the metal tube to swing at the first bending resonant frequency. The centrifugal force generated by the swinging motion will force the liquid out of the metal tube. The governing equations for the solid and fluid domains are established, and the coupling relations of the mechanical,electrical and fluid fields are described. The bending resonant frequency and bending mode in solid domain are discussed, and the liquid flow rate, velocity profile, and gauge pressure are investigated in fluid domain. The working frequency and flow rate concerning different components sizes are analyzed and verified through experiments to guide the pump design. A fabricated prototype with an outer diameter of 2.2 mm and a length of80 mm produced the largest flow rate of 13.8 m L/min at backpressure of 0.8 k Pa with driving voltage of 80 Vpp. Bysolving the electro-mechanical-fluidic coupling problem,the model developed can provide theoretical guidance on the optimization of centrifugal valveless pump characters.     

NiTi/Si薄膜驱动微型无阀泵的系统研究

介绍了形状记忆合金 /硅 (Ni Ti/Si)复合膜驱动的微型无阀泵的结构及工作原理 ,采用 Matlab对微泵的压力 P和流量 Q进行了计算和仿真 ,并将仿真结果与实验结果进行了对比。通过分析驱动膜的驱动频率与泵的几何结构对微泵性能的影响 ,得到微泵的优化方案。     

生物芯片压电微流体泵扩散管液体流量效率分析

微型扩散管是生物芯片压电微流体泵最重要的部件。它的流量效率是微流体泵关键技术之一。本文对矩形截面的微型扩散管流动进行无量纲分析 ,并采用CFD软件FLUENT对微型扩散管液体三维流动进行大量的数值实验。计算表明 ,微扩散管流量与扩散管结构几何参数 ,压强差 ,液体性质密切相关 ,并得到扩散管流量效率随无量纲参数 (雷诺数、长宽比、厚宽比和扩散角 )的变化规律和最佳流量效率的设计参数范围     

Design and fabrication of synthetic air-jet micropump

In this paper, we propose a synthetic jet-type micropump for supplying air. Synthetic jet actuators usually include a small single pumping cavity, inlet/outlet channels, and a Lead zirconate titanate(PZT) membrane that exerts the pumping pressure. To determine the optimum design parameters of the air pump, a numerical analysis was carried out by varying its geometry. The optimized air pump was fabricated by replicating PDMS parts from silicon masters patterned by the deep RIE process. The size of the fabricated micropump was 16 × 13 × 3 mm³. In order to control the frequency of the PZT membrane and reduce the controller size and power consumption, an SP4423 microchip was used. At a pumping frequency of 80 Hz, a flow rate of 9.5 cc/min, pumping pressure of 438 Pa, and power consumption less than 0.15 mW were achieved.     

3D打印的锥管坡面腔底无阀压电泵

为提高无阀压电泵的流量特性和解决泵加工工艺性差的问题,研制出了锥形流管坡面腔底无阀泵。首先,提出并设计了锥形流管坡面腔底无阀泵,分析了该泵的工作原理;然后,利用ansys软件对泵腔内流场做了模拟分析,分析结果表明该泵具有传输流体的能力;最后,利用3D打印技术制作了锥形流管坡面腔底无阀泵,并对泵的频率-流量特性进行了试验,驱动频率为8Hz时,锥形流管坡面腔底无阀泵的流量达到最大值26.8ml/min,比相同尺寸坡面腔底无阀压电泵在相同驱动电压条件下输出的最大流量增加了18.6%。试验结果表明,锥形流管坡面腔底无阀泵的流量特性优于坡面腔底无阀压电泵,且采用3D打印技术制作压电泵,提高了泵加工的工艺性,缩短了加工周期,降低了加工成本。     

微型无阀泵的数值仿真与参数设计

介绍了无阀型微泵的特点及其工作原理，针对无阀微型泵收缩/扩散口的流动特征进行了数值分析，得出了流量，压力的分布特征和关系曲线，分析了收/扩散口的几何参数对泵的输出性能的影响，采用CFD（Computational Fluid Dynamics)技术对泵内流体进行了有限元仿真，并将仿真与计算结果进行限分析比较。     

Optimisation Design of a Piezoelectric Micropump

A new aluminium based valveless fluid micropump is manufactured by the micromachining method. The pump consists of two fluid-diffuser/nozzle elements on each side of a chamber with an oscillating diaphragm which is actuated with a piezoelectric disk. The two simultaneous vibrating diaphragms produce a large oscillating chamber volume. To obtain the optimal structural parameters at the design stage of the pump, the ANSYS simulation method is used. The pump prototype with two aluminium diaphragms of ○ (with a slash) 10 mm 3 0.1 mm has been simulated. The chamber oscillating volume can be as large as 800 ml for water pumping.     

数字化无阀微泵的泵送性能实验研究

研制出一种新型的基于微流体数字化技术的数字化无阀微泵，并对无阀微泵的泵送性能进行实验研究。该微泵泵送出的液体量微小、可控，可达纳升级。针对不同粘度液体，改进驱控参数，实现了连续流、离散流的泵送。实验验证了设计原理的正确性。