平面内谐振式微悬臂梁生化传感器的设计与制造

给出了一种新型的基于平面内谐振模态的电热驱动微悬臂梁的工作原理和制造方案。相比于传统的平面外谐振模态谐振式悬臂梁,该设计能有效地降低微悬臂梁在液体中工作时的拖曳力,从而降低其振动能量损失,使得其接入锁相环接口电路后的闭环品质因数达到了249。电热驱动和压阻检测方式便于工艺集成和快速检测。本文给出了基于SOI硅片和深反应离子刻蚀(DRIE)的悬臂梁制作方案,并分别在空气和水中对悬臂梁的谐振特性进行了测试。     

谐振微悬臂梁传感器的工作原理及其在生化检测中的研究进展

谐振微悬臂梁是一种可以将质量变化转换为频率信号的微质量型传感器，因其分辨率高、灵敏度高、成本低、易于集成和小型化等优点而备受关注。谐振微悬臂梁现已被广泛应用于流量控制、生物医学痕量检测、气态和液态分子分析等领域。近年来，随着微机电系统（Micro-Electro-Mechanical System,MEMS）技术的快速发展，针对谐振式微悬臂梁传感器的研究与应用越来越多，对近年来谐振式微悬臂梁传感器在环境检测、生物医学等领域的具体应用进行了综述，并对未来的发展方向做出了展望。     

振动式微机械陀螺驱动控制电路研究

本文分析了微机械陀螺检测灵敏度和驱动信号频率和幅度的关系,在此基础上提出了一种振动式微机械陀螺驱动控制环路方案并给出了相应的电路实现方法.它利用陀螺谐振时驱动信号和驱动模态位移信号具有900相位差这一特性,采用锁相方式完成驱动轴的稳频控制,恒幅控制环节则采用半波整流电路及后续的直流电压调整电路实现,从而完成了对驱动轴的锁相和恒幅双环路控制,保证了陀螺驱动轴的谐振和振幅恒定,有效的提高了陀螺的灵敏度和标度因子的稳定性.最后针对音叉电容式微机械陀螺进行的开闭环对比实验证明,添加控制环路的检测电路零偏稳定性提高了10倍左右.     

一种高精度密度传感器的研究

圆短筒谐振式密度传感器的主要优点是适合于在线连续测量,测量精度高,易实现数字化传输,抗干扰能力强,稳定性和可靠性好.圆短筒谐振式密度传感器以圆筒谐振子为核心,基于正反馈原理,由激振元件、拾振元件、谐振子和放大电路组成高品质的闭环谐振系统.我们采用有限元法分析方法,研究计算了圆筒谐振子静力学特性和模态响应等动力学特性.设计了圆筒谐振子闭环振荡电路,单片机信号处理系统.对密度传感器进行标定和温度补偿.分析了影响测量结果的各个因素,给出了20℃时传感器测量结果的不确定度.通过实验可靠性高又实用的圆筒谐振燃油密度传感器测量精度达到0.4 kg/m.     

微机械振动陀螺仪闭环驱动电路分析与设计

为了提高微机械振动陀螺仪输出信号的灵敏度,通常要求驱动信号频率与陀螺仪驱动模态的谐振频率相匹配,且驱动信号幅值稳定.驱动电压信号要满足这些要求,必须采用闭环驱动方式.完整地推导了闭环驱动电路的内在机理,探讨了自激振荡与锁相环两种实现方式,并给出了具体的电路原理框图.     

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。     

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。     

一种扭转谐振式MEMS电场传感器

提出了一种基于微机电系统(MEMS)的扭转谐振式电场传感器。该微型电场传感器的感应电极与屏蔽电极采用共面叉指结构,首次采用扭转谐振的工作方式,显著提高了微型电场传感器的灵敏度。介绍了传感器的工作原理、结构设计、有限元仿真及实验。实验结果表明:在0～50 kV/m电场范围内,该传感器的线性度为0. 14%,3个往返行程的总不确定度优于0. 43%。在增益电阻为100 MΩ的情况下,传感器灵敏度达到4. 55 mV/(kV/m),相对已有传感器灵敏度提高了1个数量级。     

微机械悬臂梁中的机械噪声机制分析

本文采用能量统计分布方法研究微机械悬臂梁的噪声模型,对热机械噪声理论模型进行了拓展和修正,使之适用于低温和高频条件.研究了温度、压力和频率对热机械噪声、温漂噪声和吸附-脱附噪声的影响.根据研究结果对静态检测悬臂梁和动态频率响应悬臂梁传感器进行了具体分析.对于静态下工作的微机械悬臂梁,振幅的随机变化取决于热机械噪声.对于工作在谐振状态的微米尺度悬臂梁,在室温常压下热机械噪声是主要的噪声机制;当尺寸进一步缩小至纳米尺度时,表面效应变得显著,吸附-脱附噪声成为主要的噪声机制.基于对不同情况下噪声特性的分析,对微机械悬臂梁传感器的优化设计规则进行了探讨.     

解耦型静电力闭环微陀螺

微陀螺采用双框架双支撑解耦结构实现X-Y方向运动相对独立,驱动模态采用叉指电容结构实现大范围静电驱动,敏感模态方向采用差分电容作为检测接口实现高精度位置测量.X方向设计了独立的位移检测单元,而Y方向配置了静电力反馈单元,实现系统的闭环静电力反馈控制,提高传感器的性能.为分析提高系统输出精度的条件,推导出影响系统检测灵敏度的因素,改进了驱动模态闭环方案,提出了敏感模态无相差静电力反馈方法.     

Effect of thermal and mechanical properties variations on microcantilever mass sensor performance

Ensuring desirable performance for piezoelectric microcantilever sensors constitutes a crucial research subject particularly for the applications such as detection of biochemical entities, virus particles or human biomarkers. However, these sensors’ performance may be affected by the environmental conditions such as temperature variation, and/or the uncertainty in the material properties. The objective of this study is to explore Young modulus uncertainty of microcantilever’s structural layer, thermo-mechanical and geometrical temperature dependency effects, on the natural frequency, bias and sensitivity of microcantilever mass sensors. These effects have been investigated for different sensor lengths and resonant modes. Also, a temperature compensation method which omits the need for bulky non-contact thermometers or fabrication of built-in temperature sensor has been proposed. As theoretical model, Euler–Bernoulli beam theory has been employed and solved by Galerkin expansion procedure. Using this model, it is demonstrated that the sensitivity of microcantilever sensor decreases with increasing the added mass. The microcantilever sensor sensitivity operating at the second resonant mode has been improved almost five times comparing to the first mode sensitivity regardless of microcantilever length. The simulation results show that temperature variation causes thermal frequency shift which in turn introduces a significant mass bias far beyond the sensors’ minimum detectable mass. This mass bias is constant for a given microcantilever in its first and second resonant mode. Additionally, the effect of temperature variation on the sensitivity of the given mass sensors is negligible. However, it has been shown that the variations in sensors sensitivity due to uncertainty of Young modulus remain constant for different lengths and two resonant modes of the microcantilever sensor.     

A phase-locked loop frequency tracking system for portable microelectromechanical piezoresistive cantilever mass sensors

A closed-loop circuit is developed in this work for tracking the resonant frequency of silicon microcantilever mass sensors. The proposed closed-loop system is mainly based on a phase-locked loop (PLL) circuit. To lock onto the resonant frequency of the resonator, an actuation signal generated from a voltage-controlled oscillator is fed back to the input reference signal of the cantilever sensor. In addition to the PLL circuit, an instrumentation amplifier and an active low-pass filter are connected to the system for gaining the cantilever output signal and transforming a rectangular PLL output signal into a sinusoidal signal used for sensor actuation, respectively. To demonstrate the functionality of the system, a self-sensing silicon cantilever resonator with a built-in piezoresistive Wheatstone bridge is fabricated and integrated with the circuit. A piezoactuator is employed to actuate the cantilever into resonance. From the measurement results, the integrated closed-loop system is successfully employed to characterize a 9.4 kHz cantilever sensor under ambient temperature cross-sensitivity yielding a sensor temperature coefficient of ?32.8 ppm/°C. In addition to it, the sensor was also exposed to exhaled human breath condensates and e-cigarette aerosols to test the sensor sensitivity obtained from mass-loading effects. With a high frequency stability (i.e., a frequency deviation as low as 0.02 Hz), this developed system is intended to support the miniaturization of the instrumentation modules for cantilever-based nanoparticle detectors (CANTORs).     

Shear effect on dynamic behavior of microcantilever beam with manufacturing process defects

This paper is concerned with the investigation of the shear effect on the dynamic behavior of a thin microcantilever beam with manufacturing process defects. Unlike the Rayleigh beam model (RBM), the Timoshenko beam model (TBM) takes in consideration the shear effect on the resonance frequency. This effect become significant for thin microcantilever beams with larger slenderness ratios that are normally encountered in MEMS devices such as sensors. The TBM model is presented and analyzed by numerical simulation using Finite Element Method (FEM) to determine corrective factors for the correction of the effect of manufacturing process defects like the underetching at the clamped end of the microbeam and the nonrectangular cross section of the area. A semi-analytical approach is proposed for the extraction of the Young’s modulus from 3D FEM simulation with COMSOL Multiphysics software. This model was tested on measurements of a thin chromium microcantilever beam of dimensions (80 × 2 × 0.95 μm³). Final results indicate that the correction of the effect of manufacturing process defects is significant where the corrected value of Young’s modulus is very close to the experimental results and it is about 280.81 GPa.

     

基于DSP的数字磁通门传感器设计

针对传统磁通门传感器模拟电路受温度影响较大的问题,设计了一种基于DSP的数字式闭环磁通门传感器.传感器的模拟电路由AD转换器、DSP和DA转换器取代,滤波、相敏整流和积分等关键环节采用DSP软件编程实现,模拟电路的减少增强了系统的稳定性.传感器的精度和稳定性主要取决于位于反馈回路的DA转换器,采用高分辨率、高稳定的DA转换器芯片可有效提高传感器的温度性能.详细介绍了该磁通门传感器系统的硬件结构、软件设计和实验结果.结果显示:系统零点温度系数为8.9×10-7/℃,灵敏度温度系数为3.9×10-6/℃,25℃时线性度达到了9.4×10-5.     

A surface-micromachined resonant-beam pressure-sensing structure

The first study on an entirely surface-micromachined resonant-beam pressure sensor is presented. Using a fully surface-micromachined process, an encapsulated beam resonant pressure-sensor structure with a pressure-sensitive diaphragm of 100×150×2 μm has been fabricated. The resonating beam is fully enclosed inside the reference vacuum cavity formed beneath the diaphragm. The new design enables high pressure sensitivity and a miniature chip size, essential for sensors such as catheter-mounted intravascular blood pressure sensors. The pressure sensitivity is measured at 3.2%/bar with a beam resonance frequency of about 700 kHz     

Mass sensing of multiple particles adsorbed to microcantilever resonators

Microsystem Technologies - Accurate prediction of resonance frequency shift due to binding of a discrete cell to a microcantilever resonator was achieved, in closed form, by modifying the Dunkerley...     

Support loss for beam undergoing coupled vibration of bending and torsion in rocking mass resonator

Rocking mass resonator is widely used to design various sensors and actuators, which is a dual-axial symmetry resonator with high sensitivity. Q_support is the dominant energy loss mechanism influencing its high sensitivity. The anchor types and support loads applied to attachment points of rocking mass resonator are analyzed. Then support loss is simplified as a model with a beam attached to a finite thickness plate at its end. The general formulations for power radiated into support structure are given. An accurate analytical model of support loss for rocking mass resonator has been developed and verified by experiments. When the thickness of resonator is 240 μm, the measured Q can achieve a value of 589.1; while the thickness of resonator is reduced to 60 μm, the measured Q can achieve a value more than 8500. The derived model is general and might be applicable to various micro beam resonators and anchor types, providing significant insight to design of high-Q rocking mass devices.     

Optimization and comparison of photonic crystal resonators for silicon microcantilever sensors

Microcantilever sensors have been known as a fundamental design used in force sensors, strain sensors and biochemical sensors. The fast-growing applications in nanoelectromechanical systems (NEMS) lead to strong demands in new sensing mechanism in order to downsize the sensing elements to nanometer scale. Photonic crystal (PC) based resonators have been investigated as promising solutions because the bandgap structure and resonator characteristics are extremely sensitive to the deformation and position shift of holes in PC resonators. In addition to the well-known nano-cavity resonator (NCR), we proposed hexagonal nano-ring resonators (NRR) of two different layout configurations. When a microcantilever under different force loads, both of the resonant wavelength and the resonant wavelength shift can be measured as a linear function of force load. The linear relationship between wavelength shifts and strain is observed as well. The minimum detectable force and detectable strain for NRR configuration 1 is derived as small as 0.0757 μN and 0.0023%. The outstanding sensing capability renders PC resonators as a promising nanomechanical sensing element to be integrated in various transducers for NEMS applications.     

Contactless electromagnetic switched interrogation of micromechanical cantilever resonators

A principle for contactless interrogation of passive micromechanical resonator sensors is proposed. The principle exploits an external primary coil electromagnetically air-coupled to a secondary coil which is connected to a conductive path on the resonator. The interrogation periodically switches between interleaved excitation and detection phases. During the excitation phase the resonator is driven into vibrations, while in the detection phase the excitation signal is turned off and the decaying oscillations are contactless sensed. The principle advantageously avoids magnetic properties required to the resonator, thereby ensuring compatibility with standard silicon microfabrication processes. The principle has been implemented on a MEMS SOI microcantilever resonator sensor with mechanical resonant frequency of 10.186 kHz and has been demonstrated to work over a distance of up to 1 cm. Tests based on the deposition and evaporation of a water droplet have demonstrated the capability to sense physical and chemical quantities which affect either the resonant frequency or the quality factor of the resonator.     

电容式微机械陀螺双环路闭环驱动电路研究

为了提高微机械陀螺系统的检测灵敏度,对微机械陀螺系统的驱动电路进行了研究.分析了微陀螺闭环驱动系统理论,基于此提出一种双环路闭环驱动方法,并且利用数学工具simulink建立系统模型,验证此方法的可行性,最后设计完成相应电路.此方法引入锁相环实现闭环驱动电路的稳频控制;采用自动增益控制器(AGC)实现恒幅控制.利用Hspice完成电路级仿真.结果表明,微机械陀螺双环路闭环驱动电路建立稳定振荡的时间为45 ms,稳定振荡频率为2.7553 KHz,频率偏差为0.1 z,频率抖动为0.056563 Hz.相对于传统的AGC闭环驱动电路,此闭环驱动电路建立稳定振荡时间缩短了30.77%,频率稳定性是传统AGC闭环驱动电路的32.72%.微机械陀螺环路闭环驱动电路提高驱动信号性能,对于微机械陀螺检测灵敏度的提高有着重要意义.