Development of miniaturized piezoelectric actuators for opticalapplications realized using LIGA technology

To combine the advantages of the LIGA technology and piezoelectric materials, first prototypes of movable elastic LIGA structures have been realized on piezoelectric substrates. The structures consist of a flexible beam fixed to the piezoelectric substrate at its two ends in order to amplify the d₃₁-contraction of the piezoelectric substrate. By using this flexible LIGA beam as a magnification mechanism, the small displacements of the piezoelectric substrate are amplified by more than a factor of 20, offering various possibilities of applications, especially in micro-optics. In this paper, first the fabrication process and the performance of these new prototypes of LIGA piezoelectric actuators are described in detail, demonstrating the feasibility of the new concept combining the LIGA technique and piezoelectric substrates. Subsequently, LIGA-piezoelectric actuators developed for micro-optical applications are presented. These new optical actuators are also based on an elastic beam but slightly modified in order to modulate light propagating in optical fibers. They find promising applications as micro-optical attenuators or choppers whose performance is demonstrated     

压电阻抗技术用于结构健康诊断的一种方法

基于压电阻抗技术用于结构健康诊断的基本原理,以用螺栓连接固定的铝板为例,应用压电阻抗技术对结构中螺栓松动的损伤进行检测实验。鉴于以往此类实验中所采用的阻抗分析仪价格十分昂贵,提出了一种更实用的实验方法。实验结果表明:采用这种方法同样可以通过测量压电片阻抗的变化来诊断出螺栓松动的结构损伤。     

定量点胶技术的研究进展

定量点胶技术从用单纯的针筒点胶发展到目前的全自动程控点胶,点胶体积、针尖位置及点胶精确度等在控制方面有了很大突破.综述了时间/压力型点胶技术、活塞式点胶技术及非接触式蠕动泵型点胶技术,并简要介绍天津大学在定量点胶方面的研究进展.     

Dynamic characteristics of a piezoelectric driven inkjet printhead fabricated using MEMS technology

To understand the residual vibration of the piezoelectric diaphragm in a piezo (PZT) driven inkjet printhead fabricated on silicon wafers by MEMS manufacturing process, the transfer function of the piezo velocity to sinusoidal input voltage is obtained in the experiments. The piezo velocity can be predicted using the obtained velocity transfer function with discrete Fourier transform of a trapezoidal waveform. In the low amplitude of voltage waveform, the spectrum shows a good agreement between the predicted and measured velocities of the piezo diaphragm. However, when the drop is ejected from the nozzle orifice with actual amplitude of the voltage waveform, the spectrum of the piezo velocity shows more complicated frequency components due to the reflected pressure waves and fluid motion inside the chamber. In this study it has been attempted to obtain the transfer function of the piezo velocity to the voltage input when the drops are fired. The simulated results of the piezo displacement with the various durations of the voltage waveform show a good agreement with the drop volume and velocity measured in experiments. In addition, it was found that suppressing the residual oscillations was closely related to eliminating the satellite drop formation, which was confirmed with the strobe stand drop visualization.     

双通道压电式密度传感器的研究

在同一压电石英晶片上制备两个石英晶体谐振器 ,实验结果表明双通道之间的相互干扰可以忽略。在石英晶体表面修饰多孔TiO2 膜层 ,可大大提高传感器对液体密度的灵敏度。采用两个修饰不同厚度TiO2 膜层的双通道压电传感器的频率差作为测量信号 ,可以消除液体粘度的影响 ,并获得与液体密度有良好线性关系的工作曲线 ,实现液体密度的测定     

用于液相检测的双参数压电DNA传感器研究

采用自组装技术,利用亲和素-生物素系统将25-mer的生物素标记的DNA探针固定于石英谐振器金电极上,与双参数压电传感器相结合,研制成了用于液相检测的压电DNA传感器。该传感器稳定性较好,3h频移在5Hz以内;液体的体积在一定范围内对双参数传感器未见明显影响;用双参数方法制作的传感器特异性等性能较好,为实现检测的自动化和生物的动力学测定打下了基础。     

图像分析在液滴检测技术中的应用

基于图像分析的液滴检测技术对研究液体特性具有重要意义,样品液滴的形状参数是表征液滴特性的一个重要参数.设计了基于CCD摄像机图像采集的液滴检测系统,对液滴图像进行滤波、去噪、二值化等图像处理,提取宽长比、复杂度、形状参数和离心率等特征参数,结合多项式拟合和层次分析法对液滴轮廓外形进行分析.通过实验证明:在液滴检测技术中,图像技术具有现实可行性.     

压电传感测试技术的应用研究进展

压电传感器以其独特的性能在减振降噪、健康监测、形状自适应控制、损伤监测等方面发挥着重要作用,综述了压电传感测试技术在航空航天、土木、机械、交通工程、铁路行车安全监测等领域的研究进展,并指出了今后有待进一步研究的问题。     

压电微固体模态陀螺的安装技术

压电微固体模态陀螺（ PMMG）利用压电PZT长方体的某高阶共振模态作为参考振动,是一种抗冲击、抗震动能力强的新型全固态陀螺。获得优化的参考振动振型对提高陀螺性能至关重要,但是大多数文献都没有涉及到封装对参考振动的影响。利用有限元方法（ FEM）分析了压电振子安装时支撑点位置与接触面积对参考振动的影响,分析结果表明：相对于接触面积的变化,支撑点位置的变化对陀螺参考模态的影响更大。该研究结果为压电微固体模态陀螺的安装方法提供了理论基础。     

A microgripper using piezoelectric actuation for micro-object manipulation

Design, fabrication and tests of a monolithic compliant-flexure-based microgripper were performed. The geometry design and the material stresses were considered through the finite element analysis. The simulation model was used to study in detail profiles of von Mises stresses and deformation. The maximum stress in the microgripper is much smaller than the critical stress values for fatigue. The microgripper prototype was manufactured using micro-wire electrode discharge machining. A displacement amplification of 3.0 and a maximum stroke of 170 μm were achieved. The use of piezoelectric actuation allowed fine positioning. Micromanipulation tests were conducted to confirm potential applications of the microgripper with piezoelectric actuation in handling micro-objects. The simulation and experimental results have proven the good performance of the microgripper.     

压电式传感器测定蛋白质吸附动力学参数

利用液隔电极型压电式传感器实时监测牛血清白蛋白(BSA)在石英表面吸附过程。基于所提出的吸附动力学模型,估算出BSA在石英表面的吸附速率常数为ka=1.27×103mol-1·L·s-1,脱附速率常数为kd=1.31×10-3s-1,由可逆吸附态向不可逆吸附态的转化速率常数为kf=3.46×10-4s-1。     

Fluid dynamic behavior of dispensing small droplets through a thin liquid film

This paper presents a technology for dispensing droplets through thin liquid layers. The system consists of a free liquid film, which is suspended in a frame and positioned in front of a piezoelectric printhead. A droplet, generated by the printhead, merges with the film, but due to its momentum, passes through and forms a droplet that separates on the other side and continues its flight. The technology allows the dispensing, mixing and ejecting of picolitre liquid samples in a single step. This paper overviews the concept, potential applications, experiments, results and a numerical model. The experimental work includes studying the flight of ink droplets, which ejected from an inkjet print head, fly through a free ink film, suspended in a frame and positioned in front of the printhead. We experimentally observed that the minimum velocity required for the 80 pl droplets to fly through the 75 ± 24 μm thick ink film was of 6.6 m s^?1. We also present a numerical simulation of the passage of liquid droplets through a liquid film. The numerical results for different initial speeds of droplets and their shapes are taken into account. We observed that during the droplet–film interaction, the surface energy is partially converted to kinetic energy, and this, together with the impact time, helps the droplets penetrate the film. The model includes the Navier–Stokes equations with continuum-surface-tension force derived from the phase-field/Cahn–Hilliard equation. This system allows us to simulate the motion of a free surface in the presence of surface tension during merging, mixing and ejection of droplets. The influence of dispensing conditions was studied and it was found that the residual velocity of droplets after their passage through the thin liquid film well matches the measured velocity from the experiment.     

Change propagation analysis for system modeling using Semantic Web technology

Change propagation potentially affects many aspects of a SysML-based system model during the iterative process of Model-Based Systems Engineering (MBSE). However, few authors have addressed the implication of engineering change and its impact. To address having a successful change process, this article analyzes and explicitly represents different scenarios of how a system model is changed from a formal perspective, i.e., how a system model should be changed, and how model elements should be added, deleted or modified in response to design changes. A workflow is introduced to guide the change process taking change propagation into account. Second, change impact relationships among requirements, behaviors, and structures of the system model are formalized by an ontology to make the semantics both human-understandable and machine-readable. Reasoning rules are defined as well in order to improve automation of the change process. Finally, an experiment using a water distiller system showed that the identification of change impact information could help designers complete the change in less time and with higher quality.     

A finite element method for the analysis of piezoelectric composite hydrophones

A robust finite element method is developed for the analysis of piezoelectric bodies. The method is general enough to account for the losses in material coefficients. The method is used to analyze the behavior of 3:1 PZT-rubber composite hydrophone. The effect of material properties, sizes and locations of the rubber phase on the response of the composite is studied. Also the viscoelastic properties of the rubber phase are studied for its effect on the sensitivity as well as on the dynamic response of the composite hydrophone.     

Modeling analysis of a triaxial microaccelerometer with piezoelectric thin-film sensing using energy method

This study applies energy method to derive the system modeling of a triaxial microaccelerometer that consists of a quadri-beam suspension, a seismic mass, and displacement transducers using piezoelectric thin films. Two suspension beams support both ends of the seismic mass, which is fabricated by anisotropic etching of silicon. An out-of-plane acceleration will result in a symmetric bend, and in-plane accelerations will produce asymmetric bend and torsion of the suspension beams. Two piezoelectric thin-film transducers are arranged at both ends of each suspension beam. Eight transducers in total are interconnected such that triaxial accelerations can be measured selectively. The structure stiffness of the suspension beams considers both the silicon beams and piezoelectric films by the use of the laminated beam theory. Therefore, the analytical model is applicable to the accelerometers with thick piezoelectric films. The model is based on the anisotropic material properties of Silicon and PZT and Euler’s beam equation with the assumptions that smaller strains and stresses are negligible. The analytical results of the resonant frequencies and sensor sensitivities to triaxial accelerations are presented and confirmed by finite element analysis.     

基于金纳米颗粒免疫凝集的压电传感技术快速检测人血清免疫球蛋白IgG

发展了一种利用金纳米颗粒免疫凝集的压电传感技术用于人血清免疫球蛋白IgG的简单、快速、高灵敏检测.以金纳米颗粒替代传统胶乳标记羊抗人IgG诊断血清(抗IgG),利用石英晶体微天平(QCM)直接灵敏响虚因金纳米颗粒免疫凝集而引起溶液的非质量参数(密度、粘度等)的变化.考察了pH值、离子强度和抗IgG-金纳米颗粒浓度对免疫凝集反应的影响,并进行了质控实验.结果表明,该传感技术毋需固定活性组分,可快速榆测浓度下限0.38μg/mL的免疫球蛋白IgC.定量能力与经典ELISA法相接近,可基本满足临床疾病诊断的生化检测要求.     

用代码分析技术检测软件缺陷

为了查找和发现软件源代码中的漏洞和薄弱环节,进一步提高软件的质量,在深入研究代码分析技术原理的基础上,提出了代码分析技术的应用模式,从内存管理、数组越界、并发缺陷以及空指针引用或异常等多个角度进行了探讨分析,给出具体实例对代码分析技术在解决具体问题中的重要性进行论证。最后给出了代码分析技术用于检测软件缺陷的主要步骤。该研究对软件源代码的测试工作具有一定的理论价值和实际意义。     

Pneumatic dispensing of nano- to picoliter droplets of liquid metal with the StarJet method for rapid prototyping of metal microstructures

This study presents a new, simple and robust, pneumatically actuated method for the generation of liquid metal micro droplets in the nano- to picoliter range. The so-called StarJet dispenser utilizes a star-shaped nozzle geometry that stabilizes liquid plugs in its center by means of capillary forces. Single droplets of the liquid metal can be pneumatically generated by the interaction of the sheathing gas flow in the outer grooves of the nozzle and the liquid metal. For experimental validation, a print head was build consisting of silicon chips with a star-shaped nozzle geometry and a heated actuator (up to 280°C). The silicon chips are fabricated by Deep Reactive Ion Etching (DRIE). Chip designs with different star-shaped geometries were able to generate droplets with diameters in the range of the corresponding nozzle diameters. The StarJet can be operated in two modes: Either continuous droplet dispensing mode or drop on demand (DoD) mode. The continuous droplet generation mode for a nozzle with 183?μm diameter shows tear-off frequencies between 25 and 120?Hz, while droplet diameters remain constant at 210?μm for each pressure level. Metal columns were printed with a thickness of 0.5–1.0?mm and 30?mm height (aspect ratio >30), to demonstrate the directional stability of droplet ejection and its potential as a suitable tool for direct prototyping of the metal microstructures.