柔性膜微型电磁驱动器的设计与制作工艺

主要讨论了一种微型电磁驱动器的设计和制作工艺。该驱动器结构简单，由Parylene振动膜和硅基片两层组成，将驱动线圈与硅片集成在一起。对平面电磁线圈的驱动特性和驱动器振动膜的形变进行了分析，并对其关键尺寸进行优化。采用电镀工艺在硅基片上电镀驱动线圈，在Parylene薄膜上电镀NiFe合金阵列，采用牺牲层工艺得到振动膜的悬空结构。     

基于MEMS工艺的高能量密度微电磁驱动器

提出了制作高能量密度电磁驱动器的工艺方法。利用微机械(MEMS)工艺在硅片上得到多匝平面线圈和磁芯的掩模图形,接着沉积种子层铜(Cu),然后对种子层进行整体Cu的电铸;当种子层生长到20 μm左右时,剥离硅片表面的镀层并用光刻胶保护磁芯位置的镀层;再用沿线电铸的方法对线圈进行电铸;最后保护制作好的线圈镀层,电铸NiFe合金材料。在10 mm×10 mm×0.38 mm的硅片上,制作出线圈匝数22×2(铜线截面积60 μm×60 μm、总长度达1 164 mm)、NiFe合金磁芯尺寸为3 mm×3 mm×0.2 mm的高能量密度微型电磁驱动器。把这种微型驱动器应用于无阀微泵做驱动实验:通入0.3 A的正弦电流时,微驱动器产生约50 mN的电磁力。实验结果表明:这种型微电磁驱动器在相同的输入功率下,比同类其他微电磁驱动器具有更高的能量密度,能产生更大的电磁驱动力。     

Fabrication and characterization of two-chamber and three-chamber peristaltic micropumps

Two-chamber and three-chamber peristaltic micropumps with straight channels or tapered channels are fabricated by UV photolithography. Piezoelectric buzzers are chosen as actuation elements because they are cheap and have high actuation amplitude. A negative photoresistive material, SU8-25, is used as a structure material, and PDMS is chosen to bond different parts of the micropump. The effects of working phases and channel geometries are investigated and the performance of two-chamber and three-chamber micropumps is compared. The results indicate that three-chamber micropumps have better flow rates than two-chamber counterparts. For three-chamber micropumps, four-working phases have the best flow rate, six-working phased are the second, and three-working phases are the last. The channel length may have no clear effect on the flow rate, while the channel width and the angle of nozzle/diffuser have evident effects on the flow rates.     

Improved Substrate Protection and Self-Healing of Boundary Lubrication Film Consisting of Polydimethylsiloxane with Cationic Side Groups

The substrate protection and self-healing capability of a cationic polymer lubricant (CPL) on a silicon oxide surface were tested with a pin-on-disc tribometer and atomic force microscopy (AFM). CPL was made of low molecular weight polydimethylsiloxane (PDMS) containing covalently attached quaternary ammonium cations and iodide counter-anions. CPL was spin-coated on the silicon oxide surface to form a 3–4 nm thick bound-and-mobile lubricant layer. The CPL film capable of binding to the SiO₂ surface through ionic interactions is superior in substrate protection than the neutral PDMS film which cannot form the bound layer. The mobile component in the CPL film readily flows into the lubricant-depleted sliding contact region from the surrounding film. The self-healing capability of CPL via lateral flow is slightly enhanced in humid environments due to water uptake in the film. The 3–4 nm thick CPL film on silicon oxide takes 30–40 s to flow into a ~50 μm wide track, which corresponds to an apparent spreading rate of 2–3 × 10⁻¹¹ m²/s.     

A biomimetic approach for effective reduction in micro-scale friction by direct replication of topography of natural water-repellent surfaces

In this paper, we report on the replication of surface topographies of natural leaves of water-repellent plants of Lotus and Colocasia onto thin polymeric films using a capillarity-directed soft lithographic technique. The replication was carried out on poly(methyl methacrylate) (PMMA) film spin coated on silicon wafer using poly(dimethyl siloxane) (PDMS) molds. The friction properties of the replicated surfaces were investigated at micro-scale in comparison with those of PMMA thin film and silicon wafer. The replicated surfaces exhibited superior friction property when compared to those of PMMA thin film and silicon wafer. The superior friction behaviour of the replicated surfaces was attributed to the reduced real area of contact projected by them.     

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。     

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.     

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.     

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]     

基于柔性MEMS皮肤技术温度传感器阵列的研究

采用MEMS皮肤技术,在聚酰亚胺柔性衬底上成功研制出8×8阵列铂薄膜热敏电阻温度传感器。实验采用热氧化硅片为机械载体,以便于旋涂液态聚酰亚胺柔性衬底上器件的加工。最后用湿法腐蚀方法将柔性器件从载体上释放下来。试验表明聚酰亚胺衬底上的铂薄膜热敏电阻与温度的变化具有良好的线性,其电阻温度系数达0.0023/℃。与固态聚酰亚胺膜衬底相比,采用旋涂液态聚酰亚胺解决了制备中遇到的两大主要困难:其一,消除了涂聚酰亚胺衬底与载体界面之间的气泡,聚酰亚胺衬底表面能保持良好平整度;其二,制备过程中由于热循环而使柔性衬底产生的热膨胀明显减小。这种柔性温度传感器阵列易贴于高曲率物体表面以探测小面积温度场分布。     

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.     

Comparison of bonding procedures for 3D-structured polyimide films on silicon substrates applied to ink-jet cartridges

Established bubble-jet printheads consist of an assembly of three layers, which are a CMOS substrate, a channel layer and a nozzle layer. The aim of the presented work was to simplify the setup of bubble-jet printheads by means of integrating channel and nozzle structures in one single three-dimensional laser-structured polyimide nozzle plate. Different bonding techniques for an assembly onto 1/3 inch standard CMOS printhead substrates are validated. The main challenges are a variety of bonding materials, an alignment accuracy of <5 μm and the prevention of blocking the 20 μm deep fluidic channels in the polyimide which have minimal lateral dimensions of 10 μm and a minimal pitch of 15 μm. In total, three bonding techniques, with and without additional adhesion layers, were developed and evaluated. One method applies a 4 μm thick layer of Epotec 353ND (Polytec), a standard two-component epoxy, in a specifically adapted rolling manner onto the film that is subsequently aligned to the silicon chip using a flip-chip-bonder. Screen-printing and dispensing processes of adhesives were investigated but failed due to insufficient structural resolution. The second method uses photolithographic processes to produce structured adhesion preforms in SU-8 resist. With a layer thickness of 3 μm and an adapted curing schedule, promising results concerning resolution and contour accuracy were obtained. Thirdly, bonding without additional adhesion layers was achieved in a micro-sealing process that takes advantage of the highly defined thermoplastic softening of polyimide KJ (DuPont). The different processes were compared regarding to yield, printing behavior of the assembled printheads and applicability to high volume productions. The hereby developed adhesion technology was applied on the assembly of large one inch printheads for special applications.     

Fabrication and drive test of a peristaltic thermopnumatic PDMS micropump

This paper presenti, fabrication and drive test of a peristaltic PDMS micropump actuated by the thermopneumatic force The micropump consists of the three peristaltic-type actuator chambers with microheaters on the glass substrate and a microchannel connecting the chambers and the inlet/outlet port The micropump is fabricated by the spin-coating process, the two-step curing process, the JSR (negative PR) molding process, and etc The diameter and the thickness of the actuator diaphragm are 2 5 mm and 30 μm, respectively The meniscus motion in the capillary tube is observed with a video camera and the flow rate of the micro pump is calculated through the frame analysis of the recorded video data. The maximum flow rate of the micropump is about 0 36 μL/sec at 2 Hz for the zero hydraulic pressure difference when the 3-phase input voltage is 20 V.     

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。     

Design and analysis of a twisting-type thermal actuator for micromirrors

This paper reports the design of a novel twisting-type micromirror actuation system. The actuating mechanism for driving the micromirror combines two paralleled bimorph actuators bending in opposite directions for rotational control of the micromirror. Each actuator is structured by gold and silicon dioxide or nickel and silicon nitride thin films with embedded polysilicon line heaters. With a size of only 15μm in width, 1.3μm in thickness, and 100μm in length, two bimorph actuators can result in a vertical displacement of 25μm at 10 volts dc with the span of 120μm, and thus the micromirror can rotate by angles over 20°, which is a significant improvement, compared to conventional tilting-type micromirrors. This paper was recommended for publication in revised form by Associate Editor Dongsik Kim Dong Hyun Kim received his B.S. and M.S. degrees in Mechanical Engineering from Hongik University, Korea, in 2005 and 2007, respectively. Mr. Kim is currently graduate student in the department of Mechanical Engineering at Hongik University in Seoul, Korea. His research interests include micro and nanoscale heat transfer and silicon crystallization technologies for displays. Kyung Su Oh received his B.S. and M.S. degrees in Mechanical Engineering from Hongik University, Korea, in 2005 and 2007, respectively. Mr. Oh is currently a research scientist at LG Chem. Ltd. His research interests include nanoscale heat transfer, nanotubes and fuel cells and molecular simulation technology. Seungho Park received his B.S. and M.S. degrees in Mechanical Engineering from Seoul National University, Korea, in 1981 and 1983, respectively. He then received his Ph.D. degree from U.C. Berkeley, U.S.A. in 1989. Dr. Park is currently a Professor at the department of Mechanical and System Design Engineering at Hongik University in Seoul, Korea. He served as a director of general affairs of KSME. Dr. Park’s research interests include micro and nanoscale heat transfer, molecular dynamics simulation and silicon crystallization technologies for displays.     

MEMS magnetometer based on magnetorheological elastomer

To develop a simple and low-cost MEMS magnetometer, a novel sensor based on the magnetostrictive effect of magnetorheological elastomer is proposed. The micromechanical sensor consists of a silicon sensitivity diaphragm embedded with a piezoresistive Wheatstone bridge, and a magnetorheological elastomer layer attached on the sensitivity diaphragm. The interaction between the magnetic field and the elastomer generates a deflection of the sensitivity diaphragm, which changes the piezoresistance and unbalances a Wheatstone bridge. The experimental results show that the sensor has good linearity in the magnetic field range of 0-120 kA/m and the saturation magnetic field is ∼150 kA/m. This simple, low-cost, low-power sensor is easily integrated with electronic circuits using the MEMS processes.     

Optimization of P-type poly-Si thermoelectric films design

In this study, a polycrystalline silicon (poly-Si) film layer for micro thermoelectric generators (TEGs) was optimized by using Taguchi methods. An experimental plan using an orthogonal array L₉ (3⁴) is described. The fabrication process of the thermoelectric poly-Si films layer is presented in detail. The P-type poly-Si films were fabricated on a tetra ethoxy silane (TEOS) layer with a supporting Si wafer. The thermoelectric properties, Seebeck coefficient and electrical conductivity were measured, including the transport properties such as the hall coefficient, hall mobility and carrier concentration. The design parameters were optimized based on the experimental results. Using the optimum values, a p-type poly-Si films layer was fabricated and its power factor was measured. The measured power factor was 541 μWm⁻¹K⁻², which was better than the predicted value of 221 μWm⁻1K⁻².     

Micro channel forming with ultra thin metallic foil by cold isostatic pressing

The objective of this study is to establish the limit of the metal forming process in terms of size and accuracy. In the present investigation, micro channel forming with ultra thin metallic foil by the sheet metal forming process was studied. In order to examine the fabrication limit of the process, both the channel size needed to be as small as possible and the sheet thickness to be as thin as possible. Copper foil 1.0 μm thick was made into 5.6 μm wide and 3.2 μm deep channels. The shapes of the channels were straight line, concentric circle, cross, and other curved shapes. Forming was done by cold isostatic pressing. Single crystal silicon wafer was used as the die material, and die grooves were made by micro machining techniques. The die, metallic foil, and plasticine as the pressure-transmitting medium were vacuum packed in a bag made of multilayered film. The forming was conducted with a cold hydrostatic press where the forming pressure was 240 MPa. The formed channels were examined in terms of their dimensions and surface qualities. Based on the examinations, channel formability was also discussed.     

Frictional Properties of a Mesoscopic Contact with Engineered Surface Roughness

Friction between titanium spheres and an artificially structured silicon surface was measured with a friction force microscope. Two spheres with radii of 2.3 μm and 7.9 μm were firmly glued to the tip of the microscope cantilever. A periodic stripe pattern with a groove depth of 26 nm and systematically increasing groove width from 500 nm to 3500 nm was fabricated from a silicon wafer with a focused ion beam. The sphere substrate friction coefficient shows a strong enhancement at a certain groove periodicity, which is related to geometrical interlocking of the two surfaces. This shows that careful modification of the surface roughness can help to control the tribological behavior of mesoscale contacts.     

Evaluation of a wafer transportation speed for propulsion nozzle array on air levitation system

A transportation system of single wafer has been developed to be applied to semiconductor manufacturing process of the next generation. In this study, the experimental apparatus consists of two kinds of track, one is for propelling a wafer, so called control track, the other is for generating an air film to transfer a wafer, so called transfer track. The wafer transportation speed has been evaluated by the numerical and the experimental methods for three types of nozzle position array (i.e., the front-, face- and rear-array) in an air levitation system. Test facility for 300 mm wafer has been equipped with two control tracks and one transfer track of 1500 mm length from the starting point to the stopping point. From the present results, it is found that the experimental values of the wafer transportation speed are well in agreement with the computed ones. Namely, the computed values of the maximum wafer transportation speed Vmax are slightly higher than the experimental ones by about 15–20%. The disparities in Vmax between the numerical and the experimental results become smaller as the air velocity increases. Also, at the same air flow rate, the order of wafer transportation speeds is: V_max for the front-array > V_max for the face-array > V_max for the rear-array. However, the face-array is rather more stable than any other type of nozzle array to ensure safe transportation of a wafer.