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.     

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.     

A study on the MHD (magnetohydrodynamic) micropump with side-walled electrodes

This paper presents the continuous flow MHD(magnetohydrodynamic) micropump with side walled electrodes using Lorentz force, which is perpendicular to both magnetic and electric fields, for the application of microfluidic systems. A theoretically simplified MHD flow model includes the theory of fluid dynamics and electromagnetics and it is based upon the steady state, incompressible and fully developed laminar flow theory. A numerical analysis with the finite difference method is employed for solving the velocity profile of the working fluid across the microchannel under various operation currents and magnetic flux densities. In addition, the commercial CFD code called CFD-ACE has been utilized for simulating the MHD micropump. When the program was run(CFD-ACE), the applied current and magnetic flux density were set to be the variables that affected the performance of the MHD micropump. The MHD micropump was fabricated by using MEMS technology. The performance of the MHD micropump was obtained by measuring the flow rate as the applied DC current was changed from 0 to 1mA at 4900 and 3300 Gauss for the electrodes with the lengths of 5000, 7500 and 10000 μm, respectively. The experimental results were compared with the analytical and the numerical results. In addition, with the theoretical analysis and the preliminary experiments, we propose a final model for a simple and new MHD micropump, which could be applicable to microfluidic systems. This paper was recommended for publication in revised form by Associate Editor Seungbae Lee Bumkyoo Choi received a B.S. degree in mechanical engineering, M.S. in mechanical design engineering from Seoul National University, Seoul, Korea in 1981 and 1983 respectively, and PhD in engineering mechanics from the University of Wisconsin, Madison in 1992. From 1992 to 1994, he was a technical staff member of CXrL (Center of X-ray Lithography) in the University of Wisconsin where he developed a computer code for thermal modeling of X-ray mask membrane during synchrotron radiation. He is currently a professor in the Dept. of Mechanical Engineering of Sogang Univ., Seoul, Korea. His research interest includes microelec-tromechanical system (MEMS), micromatching and microfabrication technologies, and modeling issues. Sangsoo Lim received a B.S. degree in mechanical engineering from Sogang University, Seoul, Korea in 2005. He currently works at Hyundai Motors.     

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.     

具有微流量检测功能的集成微流量泵驱动结构

根据我们研制成功的铝硅双金属驱动微流量泵驱动结构的特点,本文介绍了一种实现微流量泵驱动结构与微流量传感器系统集成的方法。该方法在原微流量泵双金属驱动结构的单晶硅膜上集成制作了微流量传感器。这种一体化的集成驱动结构单元同时具有驱动功能和流量检测功能,并且制作工艺简单,为进一步实现与控制电路集成的集成微流量泵系统奠定了基础。     

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。     

相变型热驱动微泵的泵送机理研究

在简化模型的基础上 ,对泵送特性进行了理论分析 ,得到了关于泵送流量的耦合方程组 ,并通过数值计算对不同加热和冷却条件下的泵送流量关系进行了模拟。模拟结果与实验结果吻合较好 ,验证了模型的合理性。同时也证明 ,此相变型热驱动微泵的泵送机制主要来自于气体段的气塞作用及气液间巨大的密度差异     

硅微热致动泵的关键加工工艺

提出了一种新型结构的硅微热致动泵,对该泵相关的微机械关键加工工艺进行了综述分析和试验研究。     

多级低压电渗流微泵的设计、加工及测试

设计了一种多级低压电渗流微泵。该微泵系统主要由直流电源和蚀刻微通道的芯片等部分组成。芯片是在一块硅基片上蚀刻6组尺寸不同的微通道,从而达到提供不同大小的流量和承受不同背压的目的。对芯片的加工工艺流程进行了说明,同时对微泵进行了试验研究。实验结果表明：在低压下,该泵能够驱动通道中的液体。     

热驱动薄膜式微型泵的数值模拟

文中给出了对一种热驱动薄膜式微泵的数值模拟的方法与结果。     

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。     

硅微热致动泵设计及其加工工艺的研究

本文提出了一种新结构的硅微热致动泵，着重对其关键加工工艺进行了综述分析和实验研究，可为国内相关领域的研究提供一定的参考。     

微型泵的加工技术及应用

微型泵是微流体系统中的重要执行元件，标志着微流体系统的发展水平。详细介绍了微型泵的种类、加工技术、应用前景以及国内在该领域的研究状况。     

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.     

Thermal analysis of wirelessly powered thermo-pneumatic micropump based on planar LC circuit

This paper studies the thermal behavior of a wireless powered micropump operated using thermo-pneumatic actuation. Numerical analysis was performed to investigate the temporal conduction of the planar inductor-capacitor (LC) wireless heater and the heating chamber. The result shows that the temperature at the heating chamber reaches steady state temperature of 46.7°C within 40 seconds. The finding was further verified with experimental works through the fabrication of the planar LC heater (RF sensitive actuator) and micropump device using MEMS fabrication technique. The fabricated device delivers a minimum volume of 0.096 μL at the temperature of 29°C after being thermally activated for 10 s. The volume dispensed from the micropump device can precisely controlled by an increase of the electrical heating power within the cut-off input power of 0.22 W. Beyond the power, the heat transfer to the heating chamber exhibits non-linear behavior. In addition, wireless operation of the fabricated device shows successful release of color dye when the micropump is immersed in DI-water containing dish and excited by tuning the RF power.

     

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.     

热驱动薄膜式微型泵性能的初步分析

对热驱动微型泵的关键部件——铝—硅复合膜片进行了数值计算和分析。发现存在一个合适的交变加热频率范围 ,使单位时间泵腔体积变化量达到最大 ;铝膜形状取为圆形比环形有利于得到更大的泵腔变形体积。减薄硅膜厚度和增加铝膜的厚度也能增大泵腔体积变化量     

Study of fluid damping effects on resonant frequency of an electromagnetically actuated valveless micropump

As fluid flow effects on the actuation and dynamic response of a vibrating membrane are crucial to micropump design in drug delivery, this paper presents both a mathematical and finite-element analysis (FEA) validation of a solution to fluid damping of a valveless micropump model. To further understand the behavior of the micropump, effects of geometrical dimensions and properties of fluid on the resonant frequency are analyzed to optimize the design of the proposed micropump. The analytical and numerical solutions show that the resonant frequency decreases with the slenderness ratio of the diffuser and increases with the opening angle, high aspect ratio, and thickness ratio between the membrane and the fluid chamber depth. A specific valveless micropump model with a 6-mm diameter and 65-μm thickness polydimethylsiloxane (PDMS) composite elastic membrane was studied and analyzed when subjected to different fluids conditions. The resonant frequency of a clamped circular membrane is found to be 138.11 Hz, neglecting the fluid. For a gas fluid load, the frequency is attenuated by slightly shifting to 104.76 Hz and it is significantly reduced to 5.53 Hz when the liquid fluid is loaded. Resonant frequency remarkably shifts the flow rate of the pump; hence, frequency-dependent characteristics of both single-chamber and dual-chamber configuration micropumps were investigated. It was observed that, although the fluid capacity is doubled for the latter, the maximum flow rate was found to be around 27.73 μl/min under 0.4-A input current with an excitation frequency of 3 Hz. This is less than twice the flow rate of a single chamber of 19.61 μl/min tested under the same current but with an excitation frequency of 4.36 Hz. The proposed double-chamber model analytical solution combined with the optimization of the nozzle/diffuser design and assuming the effects of damping proved to be an effective tool in predicting micropump performance and flow rate delivery.     

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。