基于MEMS的静电微泵建模与仿真

对MEMS中应用广泛的静电微泵进行有限元建模分析．对于涉及多能量域下多场耦合的静电微泵建模,在仿真过程中进行了合理简化．其中在静态分析中,利用圆型薄板的小挠度变形理论和微机电系统中的静电力驱动理论来模拟静电-结构耦合过程;在泵膜的模态分析、谐响应分析以及非线性瞬态分析中,把腔内的流体当作附加质量作用在泵膜上,近似代替流场对泵膜的影响,从而减小计算量,提高了仿真效率．     

锯齿型微流道微泵流动特性分析及性能测试

通过对新型锯齿型和传统扩张／收缩型两种微流道内部流场数值分析结果进行比较,得出微流道内流动状态随雷诺数的变化情况以及漩涡产生原因：锯齿型微流道由于侧面齿形角的存在．流动过程中较传统扩张／收缩型微流道易产生漩涡,正是由于漩涡的产生使流道压力损失降低．因而新型锯齿型微流道微泵性能优于传统扩张／收缩微流道微泵．最后采用先进的硅深反应刻蚀技术（DRIE）在硅片上加工制作出两种微流道及泵腔结构,并采用硅-玻璃阳极键合以及玻璃-聚二甲基硅氧烷（PDMS）紫外线键合的方法封装出三明治结构式微泵．通过对两种微泵分别在对称和电压偏置正弦波驱动下进行性能测试．得出电压正向偏置时微泵性能仅次于对称波形驱动下微泵性能,而电压负向偏置时最差．在对称波形驱动下,新型锯齿型微流道微泵最大流量（MFR）和最大压力头（MPH）值分别为扩张／收缩微流道微泵的1．4倍和1．9倍．因此采用新型锯齿型微流道结构将使微泵性能大大提高．     

新型双向加载MEMS微执行器动力学分析

传统横向单向加载MEMS静电微执行器存在位移过小或驱动电压过大等问题.本文提出一种纵横双向加载的新型硅基静电执行器模型.基于拉格朗日-麦克斯韦方程建立了微执行器动力方程,分析了边缘漏电场对静电力的影响,基于龙格-库塔算法将所有轴向载荷等效为轴向集中载荷,并分别仿真得到了变形与驱动电压、调节电压和轴向挤压量之间的关系,结果表明当驱动电压仅为16 V时,位移高达10.861μm,远大于目前传统横向加载单向变形微执行器的位移量.通过微型制造工艺加工了微执行器,利用高频信号采集了横向极板间的电压变化量,验证了仿真结果.     

收缩管/扩张管型无阀压电微泵的动态特性研究

为了合理地预测收缩管/扩张管型无阀压电微泵泵腔压力脉动,利用流体动力学基本理论以及锥管的特点,给出了无阀微泵的动态数学模型,包括吸入和泵出模式的连续性方程以及泵腔体积变化.采用有限元分析方法,对振动薄膜的最大体积变形量进行了计算.基于微泵动态数学模型,对无阀微泵压力和流量特性进行了仿真研究,分析不同薄膜最大体积变形量和...     

两种压电驱动自吸微泵的研制与性能比较

微泵是微全分析系统中的重要单元．为解决微泵加工工艺复杂、自吸困难和可靠性低等问题，研制了两种应用于微流控系统中的压电驱动微泵．一种是将聚二甲基硅氧烷（PDMS）泵膜、单主动阀片和弹性缓冲单元集于一体的微泵，另一种是主动阀片与被动阀相结合的微泵，这两种微泵都适用于气体和液体工作物质，实现自吸，具有结构简单、易于加工及操作方便的特点．讨论了微泵的工作原理、工艺流程、工作性能及结构参数对微泵工作性能的影响，解决了加工工艺复杂、自吸困难和可靠性低等问题．在电压100V（35 Hz条件下）和零背压的工作条件下，单主动阀微泵的最大液体泵速为5000μL／min，最大背压为5 kPa；主动阀与被动阀相结合微泵的最大液体泵速5410μL／min，最大背压15kPa．后者背压与流速明显比前者的性能要好很多，尤其是背压方面．     

MEMS器件虚拟运行中运动规律求解器的设计与实现

针对虚拟运行（在器件动态模型的基础上对MEMS器件运动性能进行评测的设计工具,其作用在于建立MEMS设计参数与器件运行之间的直接联系）中运动规律的联立、求解和实时仿真等问题,分析了几种典型MEMS器件的动态模型,提出了运动规律求解器的设计原理和体系结构,其中包括三项关键技术：物理运动规律在部件库系统中的形式化表示,物理问题自动求解的推理算法,以及离线编译的优化技术。最后,设计和实现了运动规律求解器原型系统,并在该系统中测试了微泵的虚拟运行,达到了通过修改阀片设计参数和膜片驱动参数实时观察虚拟运行中状态相应变化的目标,即在微泵的设计参数与其运行之间建立了直接的关联关系。     

微泵动态模型和虚拟运行

虚拟运行是MEMS器件运行规律的图形化展示,虚拟运行的基础是器件动态模型.首先分析了微泵的静态模型.以有限元分析数据为起点,获得了膜片静态模型.随后给出了阀片的静态模型,得到变形解析表达式且只包含压力变化量.然后以静态模型为基础,从分析微泵运行机制入手,从并不充分的实验数据中得到微泵的动态运行规律.最后基于上述动态模型实现了微泵的虚拟运行,对照实测实验结果,它具有较高的精度.在虚拟环境中可以在线看到虚拟运行状态的相应变化,最终达到了在设计参数和器件运行之间建立直接联系的目标.     

铝硅双金属驱动膜片形变方向控制及其结构参数的优化

对三种典型的铝硅双金属驱动膜片结构进行了有限元分析，结果表明，铝硅双金属驱动膜片的结构参数与驱动膜片的弯曲变形方向，中心最大挠度和有效形变体积具有紧密的联系，通过不同的结构设计可以控制驱动膜片结构的弯曲变形方向，另外，通过结构参数优化，可使驱动膜片的中心最大挠度和有效形变体积达到最大值，驱动膜片的性能得到显著提高。     

PZT压电薄膜无阀微泵

介绍了一种基于PZT压电薄膜的无阀压电微泵.该微泵利用自制的压电圆型薄膜片作为驱动部件、聚二甲基硅氧烷(PDMS)作为泵膜.本文在对微豕制备工艺研究的基础上,对其性能进行了数值和实验研究.建立了基于扩张管/收缩管理论的无阀微泵的有限元模型.利用MFX-AN-SYS/CFX技术实现了对微泵的双向流固耦合分析.对微泵的锥形角、最小宽度、扩散管长度、泵腔高度进行数值计算,得到了优化参数.数值计算的结果与实际测量的数据进行了比较,验证了仿真的正确性.     

压电微泵性能的终端特性分析及其模拟研究

 根据压电微泵的结构及其功能可将其划分成6个功能块或子系统：压电片子系统、泵腔、入口阀子系统、出口阀子系统、入口通道子系统和出口通道子系统．对6个子系统建立终端特性模型，并进行有关终端特性分析．最后，将压电微泵子系统的终端特性模型进行了组合，得到整个系统的特性模型．对此进行分析，可以方便地获得压电微泵的性能特性．     

以溶胶-凝胶法PZT薄膜为驱动的微泵研制

采用溶胶-凝胶法(sol-gel)制备技术制作了Pb(Zr,Ti)O3(PZT)压电薄膜,并以PZT薄膜为驱动制作了微泵.采用了V型微阀的微泵主要利用PZT的压电效应.针对微泵的关键结构--复合驱动膜,探索了一种Si/SiO2/Ti/Au/PZT/Cr/Au多层驱动膜结构制备方法,解决了在硅基底上制备PZT薄膜的问题,同时探讨并解决了硅各向异性刻蚀微泵的微驱动腔、单向阀的工艺问题,并通过SEM照片对V型阀和多层驱动膜进行了表征.研究结果表明,采用MEMS技术成功地完成了微驱动器的研制,得到的驱动腔硅杯平坦均匀.在V型阀微泵整体设计中需要的硅片数目少,降低了器件的复杂性,可以满足功耗低、小型化和批量生产的要求.     

Fabrication and drive test of piezoelectric PDMS valveless micro pump

Abstract

Poly‐dimethylsiloxane (PDMS) valveless micropumps with single chambers and double chambers, based on a reciprocation principle, are fabricated in this work. A drive test of a piezoelectric valveless PDMS micro pump is conducted and the influence on the flow behavior of water is investigated. Applied voltage and frequency are major factors that affect the flow rate of the micropump. The flow rate of the micropump increases with applied voltage due to the increase of piezoelectric‐disk deflection. The flow rate of the micropump is found to be when the applied voltage frequency matches the first range of the resonant frequency of the PDMS micropump filled with water at 15 to 25 Hz. The maximum flow rate and the backpressure of the micropump are about 10.51 ml/min and 274.5 Pa when applying 120 Volts at 15 Hz. The maximum flow rate of the double chamber micropump at 120 Volts and 15 Hz is 2.74 ml/min which is less than the single chamber pump. When pumping at the second range of the resonant frequency of 860–1230 Hz, the flow rate of the micropump approaches zero because a lot of air bubbles are sucked into the chamber and interfere the flow of water. Experimental measurements of generation of bubbles at a wide span of frequencies that have not previously appeared in the literature are presented and discussed.     

Performance evaluation of a valveless micropump driven by a ring-type piezoelectric actuator

Presented in this paper is the study of the performance evaluation of a valveless micropump driven by a ring-type piezoelectric actuator. The application of this micropump is to circulate fuel inside a miniaturized direct methanol fuel cell (DMFC) power system. A theoretical model based on the theory of plates and shells is established to estimate the deflection and the volume change of this micropump without liquid loading. Both finite-element method (FEM) and experimental method are applied to verify this model. Using this model, the optimal design parameters such as the dimensions and the mechanical properties of the micropump can be obtained. Furthermore, various system parameters that will affect the performance of the micropump system with liquid loading are identified and analyzed experimentally. It is expected that this study will provide some vital information for many micropump applications such as fuel delivery in fuel cells, ink jet printers, and biofluidics.     

Manipulating fluid with vibrating 3D-printed paddles for applications in micropump

This paper presents a novel working mechanism of a micropump using micropaddles(MPs) to actively manipulate fluid based on 3 D printing technology. The novel working principle is systematically discussed using analysis,computation and experiment methods. A theoretical model is established to research the working mechanism and crucial parameters for driving ability, such as MPs shape, size, vibration amplitude and frequency. Two different 3 D printing techniques that simplify the multi-step process into only one step are introduced to manufacture the prototype pump for investigating the principle experimentally. A testing system is designed to evaluate the flow rate of pumps with eight different vibrating paddles. A maximum flux of 127.9 mL/min is obtained at an applied voltage of 9 V. These experiments show that the active-type mechanical pump could not only freely control flow direction but also change flux by adopting different shapes or distribution ways. The advantage of the novel micropump is the application of the MP structure into the micropump system to actively manipulate fluid with flexibility and high driving ability at fairly low power.     

基于MEMS技术的三明治结构被动阀微泵研制

为解决微泵自吸困难、难以实现流速精确控制等问题,利用MEMS技术研制出具有三明治结构和两被动阀的压电驱动微泵,其中泵腔、泵膜和阀片分别由硅、聚二甲基硅氧炕（PDMS）和SU-8构成．从理论上,分别对气体和液体微泵的工作原理、被动阀性能以及结构参数对微泵工作性能的影响进行了分析．综合两类微泵特点,提出了气液两用微泵设计方案、工艺流程及其优化方案．在不同驱动电压条件下测试了具有不同形状泵腔、不同阀口尺寸和不同类型阀片结构的微泵．实验结果表明,该微泵可用于气体和液体介质,气、液体的最大流量分别达到53．6mL／min和1280μL／min;泵腔高度影响到微泵的体积压缩比,是影响微泵自吸的一个重要因素．该泵具有结构简单、自吸、低成本、易于加工及操作方便的特点．     

Numerical study of electroosmotic (EO) flow in microfabricated EO pump with overlapped electrical double layer (EDL)

Micropump is an important component for the development of micro absorption heat pump systems. To study the performance of microfabricated EO pump with the dimension comparable to the electrical double layer (EDL), a model avoiding the use of the Boltzmann equation was developed to investigate the EO flow instead of using the Poisson–Boltzmann (PB) equation. Generally used Debye–Huckle approximation and symmetric condition are also not involved so this model can be applied in the more complicated EO micropumps. Numerical simulation was carried out to study the distributions of potential, ions and net charge density in the EO micropump. Comparison between the present model and the PB equation was conducted. Using the present model, the EO flow in the EO micropump with overlapped EDL was investigated. It shows that the flow is quite different from the channel with dimension much larger than the EDL, which exhibits plug-like flow characteristics. The errors induced by the PB equation for the pumps with different depths were evaluated. It shows that the accuracy of the PB equation is not good when the EO pump is very thin.     

Numerical Investigation of a Periodic Heating Thermal-Bubble Actuated Diffuser–Nozzle Valveless Pump

A valveless micropump actuated by thermal bubbles which generated by an electrode heater mounted with a pair of diffuser nozzles has been numerically studied by commercial CFD software FLUENT. The relationship between the net flow rate and the superheating and heat supplying frequency has been investigated. The depth of the diffuser–nozzle micropump used in current numerical simulation model is 200 μm, and the diameter of micropump chamber is 1 mm. The pair of diffuser–nozzles are with gaps expanding from 30 to 274 μm and open angles of 7°. The working fluid is methanol in present study. The results show that the pump has different optimal driving frequency with different superheating. The cycle composed of bubble growth and shrinking costs more time at higher superheating. The maximum volume flow rate and the maximum pump pressure will increase with increasing superheating, simultaneously; and the optimal pulse duty, the maximum volume flow rate and pump pressure decrease with increasing superheating. The maximum volume flow rate and the maximum pump pressure are 29.6 μL/min and 680 Pa at ΔT = 15°C, respectively.     

3D finite element analysis of electrostatic deflection of commercial and FIB-modified cantilevers for electric and Kelvin force microscopy: I. Triangular shaped cantilevers with symmetric pyramidal tips

The investigation of the nanoscale distribution of electrostatic forces on material surfaces is of paramount importance for the development of nanotechnology, since these confined forces govern many physical processes on which a large number of technological applications are based. For instance, electric force microscopy (EFM) and micro-electro-mechanical-systems (MEMS) are technologies based on an electrostatic interaction between a cantilever and a specimen. In the present work we report on a 3D finite element analysis of the electrostatic deflection of cantilevers for electric and Kelvin force microscopy. A commercial triangular shaped cantilever with a symmetric pyramidal tip was modelled. In addition, the cantilever was modified by a focused ion beam (FIB) in order to reduce its parasitic electrostatic force, and its behaviour was studied by computation analysis. 3D modelling of the electrostatic deflection was realized by using a multiphysics finite element analysis software and it was applied to the real geometry of the cantilevers and probes obtained by using basic CAD tools. The results of the modelling are in good agreement with experimental data.