ZnO压电薄膜微悬臂梁的结构设计及研究

当压力作用在ZnO压电薄膜微悬臂梁上时,产生电荷量的大小将直接决定压电传感器灵敏度的高低.根据等效截面法,推导了复合微悬臂梁所受的作用力与其产生电荷量的关系方程,为传感器标定和力的测量提供理论依据,并依据此转换方程,对压电微悬臂梁的结构尺寸进行比较分析,以提高传感器的灵敏度和分辨率.此研究为压电微悬臂梁压力传感器的结构优化设计提供了一定的参考.     

Ansys在PZT压电薄膜微传感器压电分析中的应用

研究的PZT压电薄膜微传感器采用的弹性敏感元件为微悬臂梁结构,在压电原理和材料力学理论的基础上,采用简化的等效微器件结构建立了数学分析模型,将有限元方法发展应用于压电材料的结构分析中,并运用有限元软件Ansys7.0对PZT压电薄膜微悬臂梁结构的传感性能和线性度进行了模拟,同时分析了微悬臂梁结构的几何参数对输出电压的影响,这些分析结果和解析预测是一致的。     

基于能量法的双晶压电悬臂梁发电装置机电耦合系数分析

针对双晶压电悬臂梁发电装置机电两类能量通过压电效应耦合强弱的问题,将能量法应用到双晶压电悬臂梁发电装置机电耦合系数的分析中。开展了双晶压电悬臂梁发电装置机电耦合系数的理论分析,并建立了其与双晶压电悬臂梁发电装置尺寸参数和材料特性之间的关系,对双晶压电悬臂梁发电装置机电耦合系数与其尺寸参数和材料特性的关系模型进行了实验验证和数值模拟。研究结果表明,实验值与理论解有较好的一致性,且都在压电片厚度为0.25 mm时开路电压最大,验证了该理论模型的可靠性。此外,随着压电梁厚度比的不断增大,其机电耦合系数单调递增;同时,较大的弹性模量比有利于压电梁机电耦合系数的提高,且相对于钢弹性基片,铍青铜弹性基片更有利于压电梁机电耦合系数的提高。     

超声波轴承用挤压式压电换能器的共振频率

设计了一种超声悬浮轴承用新型径向挤压式压电换能器,用于验证超声波轴承径向共振频率理论计算的正确性。基于弹性理论、压电方程和机电类比原理,建立压电换能器机电等效电路图,理论推导出了压电换能器径向振动的共振频率方程;然后,应用Matlab软件计算出了压电换能器的共振频率。采用有限元软件对已知结构尺寸的换能器进行模态分析,计算出压电换能器所需振型及该振型下的共振频率,数值仿真分析了换能器结构尺寸对换能器共振频率和径向振幅的影响。最后,设计了 一台样机,从理论、仿真及实验三方面对其共振频率进行验证。实验结果显示：换能器径向振动共振频率的理论值与实验结果相对误差为5.89%,仿真值与实验结果误差为3.53%。实验结果证明了理论计算方法的正确性,为压电挤压换能器的设计提供了理论依据。     

PZT压电式微传感器的结构优化

压电式微传感器的灵敏度除与悬臂梁的尺寸、加工工艺和压电材料本身有关外,还与悬臂梁的截面形状有关。讨论了PZT压电式压力微传感器的灵敏度与悬臂梁变截面长度和偏转角度的关系,给出在给定外力F和压电材料用量的前提下,建立含有约束的数学优化模型,并用遗传算法计算出最优变量值,使产生的感应电荷最大,从而提高微传感器的灵敏度。     

基于ANSYS的悬臂梁压电陶瓷单晶片发电特性仿真分析

以悬臂梁压电陶瓷单晶片为研究对象,对其在不同条件影响下的发电性能进行了研究。利用有限元分析软件ANSYS中的静力学耦合场分析功能,对压电模块中影响悬臂梁压电陶瓷发电装置的位移激励、结构尺寸、材料属性等相关因素进行模拟仿真,得出各因素对悬臂梁压电陶瓷发电装置发电性能的影响规律,为悬臂梁压电陶瓷发电装置的优化设计提供理论指导。     

《智能材料与结构技术》专题文章导读：半电极含金属芯压电纤维的驱动性能

建立了悬臂梁结构半电极含金属芯压电纤维新型压电弯曲驱动器的理论模型。根据第一类压电方程,推导出自由端位移、夹持力和弯曲共振频率的解析表达式,分析了金属芯性能和半径对这3个参数的影响,并把理论计算结果和有限元分析结果进行了比较。实验结果表明,悬臂梁结构半电极含金属芯压电纤维弯曲驱动器的自由端位移可达589um,央持力可达427uN,一阶弯曲共振频率为28Hz,有限元分析结果和理论值基本吻合,说明这种驱动器有较大的端部位移、较小的夹持力和较低的弯曲共振频率。     

硅基PZT压电驱动扫描微镜的设计与优化

设计并研究了一种硅基PZT压电悬臂梁驱动扫描微镜器件.这种扫描微镜采用单晶硅平面微镜面作为光扫描反射元件,由硅基压电复合弹性悬臂梁作为驱动机构控制水平微镜面偏转实现光信号的扫描.整个光扫描微器件可以阵列方式集成在单个硅芯片上,形成光扫描器阵列.采用数值有限元分析的方法模拟和优化了压电复合弹性悬臂梁驱动扫描微镜的力学性能.分析表明,微镜偏转角与压电悬臂长度和工作电压呈线性关系.在研究了影响光学扫描微镜机电性能各项因素的基础上,给出了器件结构优化的方法.     

半电极含金属芯压电纤维的驱动性能

建立了悬臂梁结构半电极含金属芯压电纤维新型压电弯曲驱动器的理论模型.根据第一类压电方程,推导出自由端位移、夹持力和弯曲共振频率的解析表达式,分析了金属芯性能和半径对这3个参数的影响,并把理论计算结果和有限元分析结果进行了比较.实验结果表明,悬臂梁结构半电极含金属芯压电纤维弯曲驱动器的自由端位移可达589 μm,夹持力可达427 μN,一阶弯曲共振频率为28 Hz,有限元分析结果和理论值基本吻合,说明这种驱动器有较大的端部位移、较小的夹持力和较低的弯曲共振频率.     

悬臂梁压电发电装置的实验研究

压电材料在外力的作用下可以产生电荷,将这部分电荷收集起来可以为微功率电器提供电能。在对单层悬臂梁压电发电装置进行实验研究的基础上,设计并制作出多层悬臂梁压电发电装置;对两种装置的实验结果进行研究分析,不仅拓宽了悬臂梁压电发电装置的谐振频带,更有效地提高了其发电能力。     

Shape effects of micromechanical cantilever sensor

Microcantilever has been increasingly used as microsensor thanks to its fast response, low cost and parallel implementation in large quantity. The principle of sensing lies in the positive correlation between the resonant frequency of microcantilever and the target mass loading. The shape of cantilever determines the resonant frequency. Therefore it plays a vital role in microsensing. In the present study three basic geometric shapes (rectangle, triangle and half-ellipse) with innovative inner cut are investigated. The micro-cantilever beams are cut to external aspect ratios of 0.5, 1, and 2, and inner cut at aspect ratios of 0, 0.5, 1, and 2, with equal sensing area. Both numerical and experimental analysis indicates that the low-aspect-ratio cantilever with high-aspect-ratio inner cut achieved high sensitivity. The half-ellipse being the highest followed by the rectangle. The results are useful for optimal shape design of a micromechanical cantilever sensor.     

A bi-material microcantilever temperature sensor based on optical readout

As one of the simplest MEMS sensors, microcantilever can sense temperature faster and more sensitively than traditional thermometers as its small size and low thermal mass. In this paper, an Au/SiNx bi-material microcantilever temperature sensor based on optical readout is presented. The deflection of the cantilever varies with the change of temperature due to the differences in thermal expansion coefficients between gold and silicon nitride. Then, the temperature could be accurately measured by detecting the deflection of the cantilever with optical lever method. By experiments, the theoretical model is verified and the temperature characteristics of the sensor are also determined. With a commercial microcantilever, the temperature resolution of the sensor is tested to be 0.02 K when 25 mm length of optical arm set. By optimizing the microcantilever parameters, the temperature resolution of the sensor could be 0.1 mK. High sensitivity makes it suitable for some special precise temperature measurements.     

Influence of the tip mass and position on the AFM cantilever dynamics: Coupling between bending,torsion and flexural modes

The effects of the geometrical asymmetric related to tip position as a concentrated mass, on the sensitivity of all three vibration modes, lateral excitation (LE), torsional resonance (TR) and vertical excitation (VE), of an atomic force microscopy (AFM) microcantilever have been analyzed. The effects of the tip mass and its position are studied to report the novel results to estimating the vibration behavior of AFM such as resonance frequency and amplitude of the microcantilever. In this way, to achieve more accurate results, the coupled motion in all three modes is considered. In particular, it is investigated that performing the coupled motion in analysis of AFM microcantilever is almost necessary. It is shown that the tip mass and its position have significant effects on vibrational responses. The results show that considering the tip mass decreases the resonance frequencies particularly on high-order modes. However, dislocating of tip position has an inverse effect that causes an increase in the resonance frequencies. In addition, it has been shown that the amplitude of the AFM microcantilever is affected by the influences of tip and its position. These effects are caused by the interaction between flexural and torsional motion due to the moment of inertia of the tip mass.     

Effect of surface conjugation chemistry on the sensitivity of microcantilever sensors

Microcantilever sensors are an offshoot of atomic force microscopy and are useful tools for effectively detecting a target biomolecule. The recognition of the target molecule on the biosensor is based on the physical bending of the microcantilever, which is driven by a specific molecular interaction between the target molecule and the sensor surface. In this study, to enhance the sensitivity of the microcantilever sensor, the sensor surface was modified through a surface conjugation method using self-assembled monolayers (SAMs) and heterobifunctional cross-linkers. After the surface modification of the microcantilever sensor, the sensitivity for L-cysteine was recorded. The detection of L-cysteine was influenced by the active site and the molecular size of the cross-linked compound attached onto the surface of the microcantilever.     

低温环境下MEMS微构件的动态特性及测试系统

研究了微机电系统(MEMS)微构件的谐振频率等动态特性在低温环境下的变化规律,从理论上分析了改变环境温度对微悬臂梁谐振频率的影响,并对低温环境下微构件的动态特性测试技术进行了研究。研制了低温环境下MEMS动态特性测试系统,采用半导体冷阱实现低温环境,利用压电陶瓷作为底座激励装置的驱动源,通过底座的冲击激励,使微悬臂梁处于自由衰减振动状态,使用激光多普勒测振仪对微悬臂梁的振动响应进行检测,从而获得微悬臂梁的谐振频率。利用研制的测试系统,在-50℃～室温的环境下对单晶硅微悬臂的谐振频率进行了测试,结果表明,随着温度的降低,微悬臂梁的谐振频率略有增大,其谐振频率的温度变化率约为-0.263 Hz/K,与理论分析的结果基本一致。该测试装置能够有效地完成在-50℃～室温环境下微构件的动态特性测试。     

碳纳米管压阻微悬臂梁红外热探测器的研究

研究了压阻复合层微机械悬臂梁红外探测器的热挠曲理论模型。利用IC工艺和微机械加工技术设计制作了一种硅/铝/碳纳米管三层微机械悬臂梁红外探测器,该探测器基于硅和铝两种材料热膨胀系数的差异,存在双物质效应,不同温度下梁的挠度不同,其形变可通过梁根部的压敏电桥检测。为提高探测器的红外吸收特性,实验探索出了在微机械悬臂梁上涂敷碳纳米管吸热层的工艺方法。实验研究了具有碳纳米管薄膜吸热层的三层微机械悬臂梁红外热探测器对红外辐射的响应规律,结果表明涂敷碳纳米管吸热层使响应灵敏度提高近一倍。     

原子力显微镜微悬臂梁品质因数的数字调控技术的研究

为了提高轻敲模式原子力显微镜的微悬臂梁的低品质因数，在分析品质因数调控技术原理的基础上，设计了基于DSP的品质因数数字调控系统。该系统结构简单，操作方便，智能性和实时性好，能够比较精确地调控微悬臂梁振动的品质因数。通过对比液体中微悬臂梁振动的频谱以及蛋白质分子的成像实验证明，该数字调控电路能够提高微悬臂梁的力灵敏度，非常适合用于对软样品的检测。     

Uncooled infrared imaging device based on optimized optomechanical micro-cantilever array

It is a major issue to improve the thermo-mechanical sensitivity of uncooled optomechanical focal plane arrays (FPAs) for infrared imaging. This work presents an optimized multi-fold interval metallized leg (IML) configuration to increase the thermo-mechanical sensitivity of an uncooled optomechanical bi-material micro-cantilever array. The inclination angle changes of the cantilever elements are measured in the IR imaging system using an optical readout with a knife-edge filtering operation in the spectrum plane. The multi-fold IML configuration consists of alternately connected unmetallized and metallized legs. With the optimized fold number, the thermo-mechanical sensitivity of a micro-cantilever array can be amplified to two times of one-fold IML for a 120 μm×120 μm element with 1 μm thick SiN_x/0.2 μm thick Au films. Room temperature objects are imaged with the fabricated FPA containing 160×160 elements and a 12-bit CCD. Further modeling analysis shows that the experimental results are well accordant with the theoretical calculation. An important practical feature of the implemented approach is its straightforward fabrication for a large FPA, without growing complexity and cost.     

Microthermogravimetry using a microcantilever hot plate with integrated temperature-compensated piezoresistive strain sensors

This paper reports thermogravimetric analysis of nanogram samples of paraffin using a microcantilever hot plate. The microcantilever hot plate has an integrated temperature-controlled heater and integrated temperature-compensated strain-sensing piezoresistors. The microcantilever vibration amplitude was measured using either a laser and a position sensitive photodiode, or using the piezoresistors. The cantilever resonance was measured as the cantilever was heated, such that the analyte mass could be measured as a function of temperature. Both optical and piezoresistive methods were employed to generate thermogravimetric curves for analytes in the range of 1-3 ng, and the results of the two methods compared well.     

Vibration response of microcantilevers bounded by a confined fluid

Hydrodynamic predictions of fluid velocity and pressure distribution are made for fluid in a confined space bounded by a vibrating microcantilever and a fixed surface. The results are used to quantify damping factors and predict frequency response amplitudes of a microcantilever vibrating near a fixed surface. The theoretical predictions of vibration response compare favorably with experimental data.