Flow behavior of liquid-solid coupled system of piezoelectric micropump

This paper employs a shallow water model and the finite element method to approximate periodical flows of a micropump to a two-dimensional thickness-averaged flow. A liquid-solid coupled system equation of the micropump is presented. Through the mode analysis of the liquid-solid coupled system, the first-order natural frequency, diaphragm vibration shape and amplitude-frequency relationship are obtained. The vibration response of the diaphragm is calculated when an external electric field is applied. Based on the thickness-averaged flow equation, the periodical flow of the micropump is studied using the finite volume method to investigate the flow behavior and flow rate-frequency characteristics. Numerical results indicate that an optimal working frequency can be obtained, at which the flow rate of the micropump achieves the maximum when the external electric voltage is fixed. __________ Translated from Journal of Hydrodynamics, 2006, 21(4): 512–518 [译自: 水动力学研究与进展]     

Performance of a serial-connection multi-chamber piezoelectric micropump

1Introduction Micropumpsaretheessentialcomponentsin micro fluidicsystemwhichhasemergedasa popularareaofresearchwiththedevelopmentof micro electro mechanicalsystem(MEMS).Sinceoneoftheearlypiezoelectricmicropumps forinsulindeliverywasfabricatedin1978,more andmoreeffortshavebeenmadeintheresearch ofmicropumps[1].Duetotheirpreciselycon trolledflowrate,micropumpspresentpromising applicationsinanalyticalchemistry,medical treatment,pharmacy,bioengineering,fuel drop generatorforautomobileheater,etc.A…     

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.     

Modeling and flow analysis of piezoelectric based micropump with various shapes of microneedle

Micropumps have been investigated as drug delivery and disease diagnostic devices. Many of these micropumps have been designed, considering primarily, available micro fabrication technologies rather than appropriate pump performance analysis. Piezoelectric and silicon based micro pumps are more popular as compared to other smart materials being explored. The microneedle is an integral part of these micropumps providing an interface between the drug reservoir and the patient’s body for extracting the blood for investigation. Blood collected in the pump chamber passes through the biosensor and gives the required investigation report. It is aimed to minimize the pain while the microneedle is inserted in the body without having any effect on the flow characteristics. Several factors affect the pain while inserting the needle, out of which shape and size of the microneedle are two important parameters. In this study we have investigated the effect of shape of the microneedle on the flow inside the micropump. A micropump design is based on the required flow at the biosensor point. All computations were carried out with water (Newtonian fluid) as the working fluid after carrying out a comparative analysis with human blood (non-Newtonian fluid). For the pentagonal shaped microneedle, the velocity at the top of the microneedle was minimum, which is beneficial in that fluid should remain in contact with the sensor for longer time.

     

Modeling nonlinear behavior in a piezoelectric actuator

A piezoelectric tube actuator is employed as a sample positioning device in Nanocut, a cutting instrument conceived to study the mechanics of nanometric cutting. Extension of functionality of the instrument as a nanometric machine tool motivates the search for an accurate model of the actuator for implementing feedback control. A simple nonlinear model describing longitudinal expansion of the piezoelectric tube actuator is presented in this paper. The model derivation is based on a non-formal analogy with nonlinear viscoelastic materials under uniaxial extension, for which the responses to a step input are similar to the piezoelectric tube. Suitability of the model structure for arbitrary inputs is tested by cross-verification between time and frequency domains. Two parameter estimation procedures are examined and the results of the experimental work for characterization, estimation and validation are presented.     

Thermo-mechanical coupled in situ fatigue device driven by piezoelectric actuator

This paper focuses on the design of a thermo-mechanical coupled in situ fatigue device driven by piezoelectric actuator. The structural resonances, transient response, grip design and thermal insulation performance of the device are discussed in detail. Micro-indentations are prepared on the specimen’s surface as embedded defects, and the deformation behaviors of the indentation subjected to cyclic strain under temperature of 530 °C are investigated. Quantitative effects of the cross-sectional area of indentation, alternating displacement amplitude and temperature on the fatigue life of copper/aluminum composite specimens are obtained, respectively. The experimental results could serve as proofs to verify the feasibility of the proposed device. This paper shows a modular example that combines piezoelectric actuator and ceramic heating components to realize thermo-mechanical coupled in situ fatigue testing.     

Propagation behavior of SH waves in layered piezoelectric plates

In this study, the propagation of SH waves in a coupled plate consisting of a piezoelectric layer and an elastic layer is analytically investigated. The piezoelectric material is polarized in the z-axis direction and perfectly bonded to an elastic layer. The mathematical model of the SH wave propagation in this plate is based on the type of surface wave solution. Dispersion relations with respect to phase velocity are obtained for electrically open and mechanically free. Numerical examples are provided to illustrate graphically and compare the variations of the phase and group velocities versus the wave number for the different layers. The thickness ratio and the properties of the two layers have a significant effect on the propagation of SH waves. The conclusions are meaningful both theoretically and practically for the design of high-performance surface acoustic wave (SAW) devices.     

基于电液动力效应的离子拖曳微泵

介绍了一种新型电子冷却系统—离子拖曳电液动力微泵,运用MEMS技术在硅片上加工了离子拖曳微泵并进行了测试,微泵由一组平面电极组成,电极的宽度为40 μm,发射极和集电极之间的间距为50 μm,共有90对电极对,每组电极对之间的距离为100 μm。微泵静压力实验以HFE7100和无水乙醇作工作流体,通过施加直流电压来驱动工作流体,当输入电压为200 V时,微泵可以得到250 Pa的静压力。实验结果表明:微泵的静压力与施加的输入电压成二次方关系,同微流道的高度成反比。实验发现工作介质的物性参数也是决定泵性能的一个重要因素,选择合适的流体可以提高整个微泵冷却系统的性能。研究还表明,微泵的性能与工作寿命和实验环境的洁净度以及工作流体提纯密切相关。     

FSDPT based study for vibration analysis of piezoelectric coupled annular FGM plate

The vibration behavior of a piezoelectrically actuated thick functionally graded (FG) annular plate is studied based on first order shear deformation plate theory (FSDPT). A consistent formulation that satisfies the Maxwell static electricity equation is presented so that the full coupling effect of the piezoelectric layer on the dynamic characteristics of the annular FG plate can be estimated based on the free vibration results. The differential equations of motion are solved analytically for various boundary conditions of the plate. The analytical solutions are derived and validated by comparing the obtained resonant frequencies of the composite plate with those of an isotropic core plate. As a special case, assuming that the material composition of core plate varies continuously in the direction of the thickness according to a power law distribution, a comprehensive study is conducted to show the influence of functionally graded index on the vibration behavior of smart structure. Also, the good agreement between the results of this paper and those of the finite element (FE) analyses validates the presented approach. This paper was recommended for publication in revised form by Associate Editor Eung-Soo Shin Farzad Ebrahimi received his B.S. and M.S. degree in Mechanical Engineering from University of Tehran, Iran. He is currently working on his Ph.D. thesis under the title of “Vibration analysis of smart functionally graded plates” at Smart Materials and Structures Lab in Faculty of Mechanical Engineering of the University of Tehran. His research interests include vibration analysis of plates and shells, smart materials and structures and functionally graded materials.     

Free vibration analysis of functionally graded coupled circular plate with piezoelectric layers

Based on classical plate theory (CLPT), free vibration analysis of a circular plate composed of functionally graded material (FGM) with its upper and lower surfaces bounded by two piezoelectric layers was performed. Assuming that the material properties vary in a power law manner within the thickness of the plate the governing differential equations are derived. The distribution of electric potential along the thickness direction in piezoelectric layers is considered to vary quadratically such that the Maxwell static electricity equation is satisfied. Then these equations are solved analytically for two different boundary conditions, namely clamped and simply supported edges. The validity of our analytical solution was checked by comparing the obtained resonant frequencies with those of an isotropic host plate. Furthermore, for both FGM plate and FGM plate with piezoelectric layers, natural frequencies were obtained by finite element method. Very good agreement was observed between the results of finite element method and the method presented in this paper. Then for the two aforementioned types of boundary conditions, the values of power index were changed and its effect on the resonant frequencies was studied. Also, the effect of piezoelectric thickness layers on the natural frequencies of FGM piezoelectric plate was investigated. This paper was recommended for publication in revised form by Associate Editor Seockhyun Kim Saeed Jafari Mehrabadi received his B.S. in mechanical Engineering from Azad University, Arak, Iran, in 1992. He then received his M.S. from Azad University, Tehran, Iran in 1995. Now he is a faculty member of the department of mechanical engineering in Azad university of Arak, Iran and PhD student of Azad University, Science and Research Campus, Pounak, Tehran, Iran. His interests include computational methods and solid mechanics such as vibration, buckling.     

Vibration control efficiency of piezoelectric shunt damping system

The piezoelectric shunt damping technique based on the direct piezoelectric effect has been known as a simple, low-lost, lightweight, and easy to implement method for passive damping control of structural vibration. In this technique, a piezoelectric material is used to transform mechanical energy to electrical energy. When applying the piezoelectric shunt damping technique to passively control structural vibration, the piezoelectric materials must be bonded on or embedded in host structure where large strain is induced during vibration, thus to ensure vibrational mechanical energy to be transformed into electrical energy as much as possible. In this paper, the concept of vibration control efficiency of a piezoelectric shunt damping system is proposed and studied theoretically and experimentally. In the study, PZT patches are used as energy converter, and the vibration control efficiency is expressed by the vibration reduction rate per area of the PZT patches. Emphasis is laid on the effect of the generalized electromechanical coupling coefficient K ₃₁ on the vibration control efficiency. Four PZT patches with different sizes are bonded on the geometrical central area of four similar clamped aluminum plates, respectively, and vibration control experiments are conducted for these plates using the R-L shunt circuit. The results indicate that the bigger the coupling coefficient K ₃₁, the larger the rate of vibration reduction, and hence, the higher the vibration control efficiency. It also shows that the vibration responses of the first mode of the plates bonded with different PZT patches can be reduced by about 30.5%, 48.58%, 85.47%, and 89.91%, respectively. It comes to a conclusion that the vibration control efficiency of the piezoelectric shunt damping system decreases with the increase of the area of the PZT patch, whereas the vibration reduction of the plate increases with the area of the PZT patch. Therefore, it is necessary to make topology optimization for the PZT patch in the vibration control utilizing the piezoelectric shunt damping technique.     

Vibration control efficiency of piezoelectric shunt damping system

The piezoelectric shunt damping technique based on the direct piezoelectric effect has been known as a simple, low-lost, lightweight, and easy to implement method for passive damping control of structural vibration. In this technique, a piezoelectric material is used to transform mechanical energy to electrical energy. When applying the piezoelectric shunt damping technique to passively control structural vibration, the piezoelectric materials must be bonded on or embedded in host structure where large strain is induced during vibration, thus to ensure vibrational mechanical energy to be transformed into electrical energy as much as possible. In this paper, the concept of vibration control efficiency of a piezoelectric shunt damping system is proposed and studied theoretically and experimentally. In the study, PZT patches are used as energy converter, and the vibration control efficiency is expressed by the vibration reduction rate per area of the PZT patches. Emphasis is laid on the effect of the generalized electromechanical coupling coefficient K₃₁ on the vibration control efficiency. Four PZT patches with different sizes are bonded on the geometrical central area of four similar clamped aluminum plates, respectively, and vibration control experiments are conducted for these plates using the R-L shunt circuit. The results indicate that the bigger the coupling coefficient K₃₁, the larger the rate of vibration reduction, and hence, the higher the vibration control efficiency. It also shows that the vibration responses of the first mode of the plates bonded with different PZT patches can be reduced by about 30.5%，48.58%，85.47%, and 89.91%, respectively. It comes to a conclusion that the vibration control efficiency of the piezoelectric shunt damping system decreases with the increase of the area of the PZT patch, whereas the vibration reduction of the plate increases with the area of the PZT patch. Therefore, it is necessary to make topology optimization for the PZT patch in the vibration control utilizing the piezoelectric shunt damping technique.     

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.     

Flow behavior control in immersion lithography

Over the past decade, immersion lithography has been the primary technology for exposure process in semiconductor manufacturing. Compared with traditional dry lithography method, this technology improves the exposure resolution greatly by inserting a high index liquid into the gap between lens and wafer surface. Keeping the immersion liquid pure and uniform as well as avoiding residual droplets during high speed scanning motion are two challenges faced by the development of immersion lithography. Contaminations, particles, bubbles, heating and stress in the liquid will destroy the continuity of the refractive index. High speed motion of the wafer during scanning may break the meniscus stability on the interface between the liquid and the gas surrounding it, and then generate residual droplets on the wafer. All above phenomena will affect the exposure performance of immersion lithography and corresponding flow behavior control methods are required to solve the problems. This paper gives a review of the studies on flow behavior control in immersion lithography, which contains two parts: studies for liquid purity and uniformity and studies for meniscus stability. In each part, the mechanism and character of the flow behaviors as well as their effects to exposure performance are presented firstly. Then, control approaches adopted by now, including material and surface modifications as well as immersion head utilization, are introduced. In addition, the challenges faced in future studies are also pointed out. The purpose of this review paper is to help the researchers to understand the flow control problems in immersion lithography and to provide better control approaches for exposure performance improvement.     

Finite element modelling for a piezoelectric ultrasonic system

In this paper, a three-dimension (3-D) mechanical element with an extra electrical degree of freedom is employed to simulate the dynamic vibration modes of the linear piezoelectric, piezoelectro-mechanic and mechanical behaviors of a metal disc structure embedded with a piezoelectric actuator. In piezoelectric finite element formulation, a discretized equation of motion is developed and solved by using the integration scheme to explain why an adaptive boundary condition, a simple support condition with three non-equal-triangular (120°–90°–150°) fixed points near the edge, which is the asymmetric disc used as the stator of the studied ultrasonic motor, for the mechanical design of an asymmetric disc-type piezoelectric ultrasonic stator, is defined so that a lateral elliptical motion of the contact point between stator and rotor can be realized for driving the rotor. It starts from hybrid elements with displacement and electric potential as the nodal d.o.f.s model and uses Guyan reduction and Householder-Bisection inverse iteration to find the displacement profile and displacement vector flow of the stator under frequency driving. The standing wave existence is also proven by the displacement patterns of the finite element theoretical model.     

压电陶瓷微纳米伸缩量测试系统

介绍了一种压电陶瓷的微纳米伸缩量的测试系统。该系统是通过调节加在陶瓷管内外管壁上的电压变化来实现陶瓷管的伸缩,其驱动电压由计算机编程并经过D/A转换后输出,再依次通过低压和高压放大后加在陶瓷管壁上。压电陶瓷的伸缩量则由电感测微仪进行测定。实验结果表明,利用该系统可以很方便地测量压电陶瓷管的伸缩,其伸缩量随着电压的变化而变化,但并非成简单的线性关系,而是呈一条曲线。     

压电双晶片驱动的仿生柔性扑翼机构研究

分析了昆虫的翅膀-胸部运动系统,并以此为基础,仿生设计出压电双晶片驱动,柔性双摇杆机构放大位移并带动仿生翅拍动的扑翼系统.分析了压电双晶片的工作原理,讨论了柔性四杆机构的自由度和运动学,并对整个系统的准静力学进行探讨,以确定能否产生足够的力克服空气阻尼.仿真和实验结果表明,通过柔性机构放大压电双晶片位移,能实现仿生翅所需运动,同时进一步的优化设计将有助于改进扑翼机构的运动性能.     

基于动态模糊系统模型的压电陶瓷驱动器控制

针对压电陶瓷驱动器(PZT)的迟滞非线性对周期性超精密跟踪精度的影响,对基于Takagi-Sugeno(T-S)型模糊规则的动态模糊系统( DFS)前馈+PI控制方法进行了研究。介绍了DFS模型前提部分和结论部分的辨识方法; 结合直接逆模型控制和迭代学习控制的思想,提出了周期性轨迹跟踪的DFS前馈+PI控制方法。最后,针对20 Hz的三角波和正弦波期望轨迹进行了跟踪控制实验。实验结果表明：提出的控制方法对三角波和正弦波期望轨迹的最大跟踪误差分别为0.25%和0.27%,相对于PI控制,跟踪精度分别提高了52倍和64倍,而最大跟踪绝对误差分别降低到5.1 nm和5.5 nm。结果显示这种控制方法易于实现,周期性轨迹跟踪精度高。     

Frequency analysis of a tower-cable coupled system

This study considers the prediction of natural frequency to avoid resonance in a wind turbine tower-cable coupled system. An analytical model based on the Rayleigh-Ritz method is proposed to predict the resonance frequency of a wind turbine tower structure supported by four guy cables. To verify the validity of the analytical model, a small tower-cable model is manufactured and tested. The frequency and mode data of the tower model are obtained by modal testing and finite element analysis. The validity of the proposed method is verified through the comparison of the frequency analysis results. Finally, using a parametric study with the analytical model, we identified how the cable tension and cable angle affect the resonance frequency of the wind turbine tower structure. From the analysis results, the tension limit and optimal angle of the cable are identified.