压电微悬臂梁气体传感器静态弯曲模型的研究

压电微悬臂梁是一种灵敏度高、尺寸小的生化传感器.分子或原子在压电微悬臂梁功能化表面的吸附会引起悬臂梁的静态弯曲,通过静态变形可以得到微悬臂梁的表面应力.将表面应力引起的微悬臂梁中性层位置的变化引入建模过程,并与能量法相结合,建立了压电微悬臂梁在单分子层吸附稳定后的静态弯曲理论模型.结果发现在相同吸附表面积和吸附量条件下...     

应力型微悬臂梁生化传感器响应机理研究进展

针对静态微悬臂梁表面特异性结合产生表面应力信号的响应机制问题,介绍了微悬臂梁生化传感器的工作原理,阐述了应力响应机制的简化模型,从纵向界面上和横向分子间2个方面对特异性吸附引起的悬臂梁表面应力的变化进行了剖析,讨论了界面能变化、位阻作用、静电力、氢键作用等与表面应力大小及方向之间的关系,总结了应力型微悬臂梁生化传感器的响应机理的研究。     

微悬臂梁谐振式气体传感器研究进展

微机械谐振式传感器已经成为微型机电系统(MEMS)领域的研究热点。讨论了微悬臂梁谐振式气体传感器的工作原理,介绍微悬臂梁表面修饰的关键技术、主要方法和基于微悬臂梁的谐振式气体传感器领域的研究状况以及近五年以来该领域的研究进展,并对基于微悬臂梁的谐振式气体传感器的发展方向和应用前景做了展望。     

基于微悬臂梁的生化传感器

由微机械加工技术和集成电路工艺制作的微悬臂梁,通过在其表面修饰以生化敏感层,能将电、热、应力和化学等信号变化转换成一个机械响应,配合以信号采集电路和测量系统,能够达到很高的灵敏度和精度。回顾微悬臂梁作为传感器的发展历程,介绍悬臂梁的工作原理,微梁的激励、检测方法以及基于微悬臂梁阵列传感器的优点,总结了世界上硅基微悬臂梁生化传感器的最新动态,并且展望微悬臂梁传感器这一新领域的应用前景。     

用于阶跃升温的自控装置

催化剂的热脱附法已被广泛用来研究催化剂的表面非均匀性和活性中心分布,它还可以从能量的角度研究催化剂与吸附质之间的吸附形态和吸附键的强弱。热脱附法可在等温下进行,亦可用程序升温的方法进行。采用阶跃升温,使催化剂在等温下进行热脱附,得到的数据容易分析和处理,结果比较准确,但由于实现阶跃升温比较困难,目前国内外大都使用程序升温法进行热脱附。     

基于锁相环接口电路的高性能扭转谐振模态微悬臂梁传感器研究

扭转谐振模态微悬臂梁低能耗、高品质因数的特性,使它比传统的弯曲模态悬臂梁拥有更高的灵敏度和分辨率.将微传感器加工技术和生物检测技术相结合,利用扭转谐振模态微悬臂梁传感器对生物素和亲和素的特异性反应进行检测,结果传感器的灵敏度为0.9 pg/Hz,分辨可达到49 fg.本文还着重介绍了为谐振梁传感器设计的以锁相环(Phase-Locked Loop简称PLL)为核心的闭环接口电路,分析了悬臂梁和电路在闭环系统中的工作特性,并探讨了解决谐振式传感器在使用中常见的稳定性差、噪声干扰强等问题的方法.     

开孔变截面微悬臂梁传感器的等效刚度和固有频率

研究新型开孔变截面微悬臂梁传感器的等效法向刚度及其对固有频率的影响.首先,考虑微梁纵截面孔洞结构引起的弯扭耦合效应,利用二次积分法获得在自由端集中载荷作用下悬臂梁的挠度,基于弹性材料的Hooke定律建立了微梁等效法向刚度分析的解析模型.然后,采用Rayleigh法获得了微梁的固有频率.最后,通过比对实验结果和有限元结果对解析模型进行了验证.研究表明:解析模型对于开孔变截面微梁刚度和频率的预测和标定具有较好的精度;微梁的等效刚度和固有频率与跨宽比负相关,却与内外宽度比正相关.有关结论可为新型变截面微纳机械传感器的设计提供理论依据和参考.     

虚拟环境中微加速度传感器建模及拟实运行

对虚拟环境中微加速度传感器建模及拟实运行进行了研究.此微加速度传感器采用悬 臂梁式结构.论文分析了其静态特性和动态特性,建立了悬臂梁变形模型和微加速度传感器动 态行为模型;讨论了在修改结构尺寸过程中,梁长、梁厚对微加速度传感器的影响,并优化了结 构参数;最后建立虚拟环境,进行拟实运行,验证设计结果.     

PT种子层对微力传感器性能的影响

为了提高微牛顿量级微力传感器的灵敏度,比较了有PT种子层和无PT种子层的PZT压电薄膜对微力传感器性能的影响。运用Sol-Gel(溶胶-凝胶)法制作了PZT和PT/PZT/PT薄膜,采用X射线衍射技术表征了PZT和PT/PZT/PT两种薄膜的成相特征,用半导体参数测试仪测试了PZT和PT/PZT/PT两种薄膜的漏电流。结果表明,在同为600℃退火温度下,两种薄膜均具有钙钛矿结构,而且PT/PZT/PT薄膜沿(100)晶向强烈取向。当外加电压增加时,PZT薄膜的漏电流基本保持不变;PT/PZT/PT薄膜的漏电流变化在1nA左右。最后应用MEMS工艺分别制作了基于PZT,PT/PZT/PT压电薄膜微悬臂梁结构的微力传感器,并在静态和准静态下对微力传感器的传感特性进行了测试。测试结果表明,添加PT种子层对微悬臂梁的弹性系数基本没有影响,但微悬臂梁的灵敏度显著增加。     

乙基纤维素修饰的超高交联吸附树脂对四环素的吸附行为

通过Friedel-Crafts反应和化学修饰反应制备了乙基纤维素修饰的超高交联吸附树脂ECMR,采用傅里叶变换红外光谱和比表面及孔径分析对树脂结构和表面参数进行分析表征。通过静态吸附.脱附、吸附动力学和小柱吸附-脱附实验探讨了ECMR树脂对四环素的吸附行为。结果表明:ECMR树脂的BET比表面积为1083.9m~2/g,微孔面积为885.7 m~2/g。与NDA150相比,ECMR树脂对四环素具有更好的吸附性能,2种树脂对四环素的吸附量均随着温度升高而增加,吸附过程存在着较强的不可逆的化学吸附作用。2种树脂对四环素吸附动力学过程符合准一级方程,颗粒内扩散是吸附过程的主要控制步骤。小柱吸附-脱附结果表明ECMR:树脂对四环素的饱和吸附量较大,Methanol/4%NaOH(V_1/V_2=1/1)的溶液能够很好的使ECMR树脂再生。     

Structure design and fabrication of a novel dual-mass resonant output micromechanical gyroscope

A novel dual-mass resonant output micromechanical gyroscope is proposed which utilizes resonant sensing as the basis for Coriolis force detection instead of displacement sensing. It can overcome the shortcoming of single-mass resonant output micromechanical gyroscope and can reduce the common mode acceleration error by using a dual-mass topology structure and lever differential mechanism. The structure and operating principle of the device are introduced. Moreover, some important theoretical analyses of the gyroscope are provided in detail. The analytical results have shown that the resonant frequencies of vibrating mass and double-ended tuning fork resonators are 3.153 and 62.853 kHz. The device has a frequency sensitivity of 12.535 Hz/deg/s and a mechanical noise floor of $ 7.957\deg /{\text{h}}/\sqrt {{\text{Hz}}} A novel dual-mass resonant output micromechanical gyroscope is proposed which utilizes resonant sensing as the basis for Coriolis force detection instead of displacement sensing. It can overcome the shortcoming of single-mass resonant output micromechanical gyroscope and can reduce the common mode acceleration error by using a dual-mass topology structure and lever differential mechanism. The structure and operating principle of the device are introduced. Moreover, some important theoretical analyses of the gyroscope are provided in detail. The analytical results have shown that the resonant frequencies of vibrating mass and double-ended tuning fork resonators are 3.153 and 62.853 kHz. The device has a frequency sensitivity of 12.535 Hz/deg/s and a mechanical noise floor of 7.957deg/\texth/?{\textHz} 7.957\deg /{\text{h}}/\sqrt {{\text{Hz}}} in air. The finite element simulation results verify the accuracy of analytical algorithms. The common mode acceleration error of device can be reduced by 97.6%. The device is fabricated by SOG (Silicon on Glass) micro fabrication technology. Some important performances are measured by experimental method. The micromechanical gyroscope can be used to estimate the rotation rate by further implementing the signal processing electronics.     

振动轮式微机械陀螺仪闭环驱动控制方法研究

本文在分析振动轮式微机械陀螺仪稳定工作条件的基础上,探讨了微机械陀螺仪对驱动电路的控制要求,提出一种新颖的驱动频率自动跟踪的控制方法,给出了驱动电路闭环控制框图,详细分析了驱动模态闭环控制逻辑,最后的开、闭环对比实验说明了本控制方案的有效性。     

A system for the dynamic characterization of microstructures

This paper describes a fully automated measurement system designed to evaluate the dynamic characteristics of micromechanical structures (millimeter dimensions). To validate the system, vibration measurements have been carried on two structures-a micromachined silicon cantilever and bridge-and the results are presented. Out-of-plane measurements show that for the cantilever, both the mode shapes and resonant frequencies agree with beam theory predictions. However, for the bridge structure, tension due to boron doping causes a change from beam-like behavior and a more complex model is required. Mode-shapes natural frequencies and modal damping are determined from data obtained by vibrating the structures using a piezoelectric mounting system and deriving the transfer function between the piezodrive voltage and beam vibrational velocity     

低热机械噪声MEMS加速度计设计

介绍了一种能够在大气条件下具备低噪声、高灵敏度特性的MEMS加速度计设计、制作与测试.器件采用梳齿电容检测方法,利用MEMS体硅加工工艺,实现了210对梳齿的加速度计制作.该加速度计不需要真空封装和阻尼孔就能实现低热机械噪声特性,其理论热机械噪声为0.018μg/√Hz.加速度计芯片在大气封装和无阻尼孔情况下Q值高达4...     

From MEMS devices to smart integrated systems

The smart integrated systems of tomorrow would demand a combination of micromechanical components and traditional electronics. On-chip solutions will be the ultimate goal. One way of making such systems is to implement the mechanical parts in an ordinary CMOS process. This procedure has been used to design an oscillator consisting of a resonating cantilever beam and a CMOS Pierce feedback amplifier. The resonating frequency is changed if the beam is bent by external forces. The paper describes central features of this procedure and highlights the design considerations for the CMOS-MEMS oscillator. The circuit is used as an example of a “VLSI designer” way of making future integrated micromechanical and microelectronic systems on-chip. The possibility for expansion to larger systems is reviewed.     

Interferometric study of reliability of microcantilevers driven by AlN sandwiched between two metal layers

Micro-electro-mechanical systems are exposed to a variety of environmental stimuli, making a prediction of operational reliability difficult. Here, we investigate environmental effects on properties of piezoelectrically actuated microcantilevers, where aluminum nitride is used as actuation material. The environmental effects to be considered include thermal and humid cycling, as well as harsh electrical loading performed under normal conditions. Investigated properties are defined for the static and dynamic behavior of microcantilevers. A Twyman-Green interferometer, operating in both stroboscopic regime and time-average interferometry mode, is used as a metrology tool. The initial deflection and frequency changes of the first resonance mode of the microcantilevers are monitored during accelerated thermal aging tests, humidity tests, as well as harsh electrical loading and fatigue tests. Finally, the resonant fatigue tests accelerated by application of a high voltage are accomplished to evaluate a lifetime of microcantilevers. Monitoring the micromechanical behaviors of devices driven by aluminum nitride during the lifetime tests assists monitoring of their long-term stability. Finite Element Modeling is used to identify critical areas of stress concentration in the cantilever structure and to further explain various failure mechanisms.     

Dynamic analysis of torsional resonance mode of atomic force microscopy and its application to in-plane surface property extraction

In the torsional resonance (TR) mode of atomic force microscopy (AFM), the changes in the torsion-related dynamic characteristics of a tip–cantilever system due to in-plane (lateral) tip–sample interaction are used for surface property imaging. This paper investigates the fundamental dynamics of a tip–cantilever system when it is operated in TR mode, with or without tip–sample interaction. With the actual location of the tip on the cantilever taken into consideration, modal analysis is carried out to obtain the cantilever TR frequencies/mode shapes under linear elastic tip–sample interaction. The relations of lateral contact stiffness and viscosity to torsional amplitude/phase shift are established. A comprehensive understanding on the effects of lateral contact stiffness and viscosity, driving frequency, and tip location on the cantilever torsional amplitude/phase shift is achieved by parametric analysis. The basic methodology to extract in-plane surface properties in TR mode is described. This work will help in advancing the development and applications of the techniques and instruments using TR mode of AFM.     

Frequency-Dependent Electrical and Thermal Response of Heated Atomic Force Microscope Cantilevers

This paper investigates the electrical and thermal response of the heated atomic force microscope (AFM) cantilevers in the frequency range from 10 Hz to 1 MHz. Spectrum analysis of the cantilever voltage response to periodic heating distinguishes different thermal behaviors of the cantilever in the frequency domain: the cantilever voltage at low frequencies is modulated by higher-order harmonics, and at high frequencies it oscillates with 1-omega only. A simple model facilitates the understanding of complicated electrical and thermal behaviors in the cantilever, thus, it is possible to determine the cantilever temperature. The calculation predicts that temperature oscillation is restricted to the heater region when the cantilever is operated at about 10 kHz, suggesting that the periodic-heating operation of the cantilever may be employed for highly sensitive thermal metrology     

Reliability investigations in micromechanical devices

Fatigue limited lifetime of micromechanical structures has been investigated. To determine the maximum cycle number up to failure a modified Paris equation has been used to model crack growth under load. Test structures (cantilever beams) with well-defined pre-cracks were externally loaded at resonance frequency. Single crystalline silicon as functional material (bulk micromachining) was investigated. Measured and simulated critical stress intensity factors are strongly correlated for all investigated test structures and for different crack lengths showing the validity of the used model. Lifetime decreases exponentially for loads approaching a critical stress intensity. Using the experimental results determined at test structures and the simulation model, fatigue limited lifetime of micromechanical device with typical, process induced crack distribution can be extrapolated.     

High-speed imaging by electromagnetic alloy actuated probe withdual spring

This paper describes a magnetically actuated cantilever with dual spring (cantilevered actuator and torsional cantilever) for a high-speed imaging of atomic force microscopy (AFM). A fabricated cantilever beam with a high resonant frequency is successfully actuated by electromagnetic force. A planar coil is placed on the free end of the cantilever beam and embedded in a groove formed on the silicon cantilever to get a large deflection. Static and dynamic mechanical characteristics of the fabricated probes have been measured. The experimental results of the mechanical properties are compared with the calculation results obtained from a finite element method. When flowing a current of ±10 mA, a static deflection of ±2 can be achieved by a cantilever with a length of 400 μm. The scanning speed of AFM is increased up to 1 mm/s by actuating the high resonant frequency cantilever in constant force mode